HomeMy WebLinkAboutBOCC Packet 04142010 WeedsAGENDA ITEM SUMMARY
REGULAR MEETING DATE: April 14, 2010
AGENDA ITEM TITLE: Ordinance Adopting the Revised Noxious Weed Management Plan
and Repealing and Reenacting Title 6, Section 6.23 (Noxious Weeds) of the Pitkin County Code.
STAFF RESPONSIBLE: Crystal Yates -White
ISSUE STATEMENT:
The Colorado Noxious Weed Act requires each County to update the County Noxious Weed
Management Plan (WMP) every three years. Staff and the Pitkin County Weed Advisory Board
(WAB) have revised the plan and are seeking approval of an ordinance adopting the revised version.
BACKGROUND:
The current version of the WMP was adopted by the Board in 2006.
Since that time, new weeds have been found in Pitkin and surrounding counties, recommended
management strategies have changed (in particular, with regard to the understanding, availability,
and spectrum of Biological Control agents), and the size and location of current infestations has
changed (some have been eliminated, while others have grown). Staff and WAB members have
updated the plan to reflect these changes.
Staff has received feedback from the public over the last several years that the current plan is
cumbersome and difficult to use practically for small -acreage weed control. Thus, the revised
document contains changes which attempt to make the document a more readable tool for the public,
while retaining important legal content.
In addition, the 2006 document was not codified correctly and contained several inaccuracies and
typos. These errors have been rectified in the revised version.
These changes are detailed in the attached Ordinance for the Board's review.
LINK TO STRATEGIC PLAN:
The revised WMP is a product of close collaboration with the WAB, BLM, Forest Service, and local
municipalities, and reflects citizen input gathered over the last three seasons. This process supports
the Community Involvement strategic area by addressing the Strategic Goals of fostering successful
public process, broad awareness of county -wide issues, and strong community relationships.
Moreover, the improved document itself addresses Environmental Protection, by both guiding the
Pitkin County Noxious Weed Management program and providing citizens with the information to
make safe, informed, and sufficient noxious weed management plans for their own properties.
KEY DISCUSSION ITEMS:
• Is the document readable, clear, concise, and adequate?
• Does the Board approve the addition of Section 6.32.06: Pitkin County Weed
Watch List and the reorganization of other sections, as detailed in the Ordinance?
• Does the Board approve the Ordinance?
BUDGETARY IMPACT: No Impact.
RECOMMENDED BOCC ACTION: Review Ordinance and revised WMP; set Ordinance for
Second Reading and Public Hearing on April 14, 2010.
ATTACHMENTS:
• 2010 Revised Noxious Weed Management Plan
• Ordinance Adopting the Revised Noxious Weed Management Plan
ORDINANCE OF THE BOARD OF COUNTY COMMISSIONERS
OF PITKIN COUNTY, COLORADO,
ADOPTING THE REVISED NOXIOUS WEED MANAGEMENT PLAN AND
REPEALING AND REENACTING TITLE 6, SECTION 6.32 (NOXIOUS WEEDS) OF
THE PITKIN COUNTY CODE
ORDINANCE NO. -2010
WHEREAS:
1. Pitkin County adopted the Pitkin Noxious Weed Management Plan (the "Plan"), in
November 1999 by Ordinance # 99-48, and the Plan was adopted by The Town of
Snowmass Village and The City of Aspen through the Pitkin County Noxious Weed
Management Plan Intergovernmental Agreement dated March 8th , 2000.
2. The County, City of Aspen, and Town of Snowmass Village have agreed through The
Pitkin County Noxious Weed Management Plan Intergovernmental Agreement, section
4.01, to authorize the Board of County Commissioners to have the sole and final authority
to approve, modify, or reject the Plan.
3. The Plan has been revised by the Pitkin County Weed Advisory Board and Pitkin County
Land Management Staff as follows:
a. The entire document was codified correctly and reformatted.
b. Acknowledgements were updated.
c. Section 6.32.01 (Introduction) was edited for concision, accuracy, and readability,
including the addition of section 6.32.01.D (How to use this Plan).
d. Definitions were moved from the end of the document to Section 6.32.02.
e. Section 6.32.03 (Colorado Noxious Weed List) was edited to more clearly and
accurately explain State -designated Lists and Management Strategies.
f. Two weeds were added to Section 6.32.04 (Pitkin County Noxious Weed List).
Cypress Spurge (Euphorbia cyparissias) is a List -A species, designated by the
State for Eradication from all counties in Colorado. Sufur Cinquifoil (Potentilla
recta) is a List-B species, designated by the State for Containment within specific
parts of Pitkin County.
g.
Section 6.32.05 (Descriptions of Noxious Weeds in Pitkin County) was updated
for clarity and accuracy to include more up-to-date management and location
information, and to correct inaccuracies.
h. Section 6.32.06 (Pitkin County Weed Watch List) was added.
i. Section VIII: Jurisdictional Overview of Areas in Pitkin County in the current
Plan was renamed and codified as Section 6.32.07 (Early Detection, Rapid
Response) and rewritten to more specifically describe how the Early Detection,
Rapid Response approach will be used to prevent and eliminate particular
infestations in Pitkin County.
j. Section 6.32.08 (Enforcement) was revised for concision and accuracy. The
Enforcement Flowchart tool was recreated for readability and accuracy.
k. Section X: Priorities and Section XII: Plan of Work in the current Plan were
consolidated and updated as Section 6.32.09 (Priorities and Goals). Maps of
State -designated containment areas were included.
1. Section 6.32.10 (Additional Rules) was simplified. It now explains that re -
vegetation requirements exist in conjunction with various permit and land use
applications and references the County Code.
m. Information about escaped ornamentals and native thistles, the Landowner
Management Plan form, and the Resource Directory were all moved out of the
primary document into respective Appendices.
n. Section XIV: Repeal of Conflicting Provisions in the current document was
eliminated, per the direction of the County Attorney's office.
4. Copies of the Plan are available for inspection at the office of Public Works, 76 Service
Center Road, Aspen, Colorado 81611, (970-920-5390) and also at the Clerk and
Recorder's Office, Jeanette Jones, at 530 East Main Street, Aspen, Colorado 81611,
during regular business hours.
NOW, THEREFORE, BE IT ORDAINED by the Board of County Commissioners of Pitkin
County, Colorado that:
1. The revised Pitkin County Noxious Weed Management Plan is adopted.
2. Ordinance # 99-48 remains in full force and effect with respect to the Plan as amended
herein.
3. Title 6, Section 6.32, Noxious Weeds is hereby repealed and reenacted to update and
revise the Pitkin County Noxious Weed Management Plan.
INTRODUCED, FIRST READ, AND SET FOR PUBLIC HEARING ON
, 2010.
2
NOTICE OF PUBLIC HEARING AND
ASPEN TIMES WEEKLY ON
ADOPTED AFTER FINAL READING
, 2010.
PUBLISHED BY TITLE AND SHORT
TIMES WEEKLY ON
ATTEST:
By
Jeanette Jones
Deputy County Clerk
APPROVED AS TO FORM:
John Ely, County Attorney
THE FULL ORDINANCE PUBLISHED IN THE
, 2010. (Use Sunday's date)
AND PUBLIC HEARING ON
SUMMARY, AFTER ADOPTION, IN THE ASPEN
, 2010. (Use Sunday's date)
BOARD OF COUNTY COMMISSIONERS
By:
George Newman, Chair
Date:
MANAGER APPROVAL
Hilary Fletcher, County Manager
3
PITKIN COUNTY
NOXIOUS WEED MANAGEMENT PLAN
Last Revised: November 2009
Acknowledgements
Pitkin County would like to acknowledge the Pitkin County Weed Advisory Board (WAB) who
invested many hours of their time in preparing and implementing the Pitkin County Noxious
Weed Management Plan and its revisions. These past and present WAB members include:
Chonnie Bliss, Tish Bartlett, Steve Child, Ann Larson, Jim Lewis, Connie Knuth, and Amber
McKeague.
Grateful acknowledgement goes to the Pitkin County Attorney's Office for their extensive
knowledge and legal expertise.
Thank you to Lisa Tasker (E.M. Ecological, LLC), Janis Huggins (Colorado Native Heritage
Program and author of Wild at Heart), and Ann Larson for photos used in this plan. Photos were
also acquired from the Colorado Department of Agriculture website and fact -sheets, from
Forestrylmages.com and from the Wikimedia Commons website.
Thanks to each of the following agencies for reviewing the Plan and providing feedback to help
create a comprehensive Plan: City of Aspen; Town of Snowmass Village; Town of Basalt;
Pitkin County Open Space and Trails; Eagle, Garfield, and Gunnison Counties; Colorado
Division of Wildlife; Colorado Department of Transportation; Colorado Department of
Agriculture; Bureau of Land Management; United States Forest Service.
Thanks are also extended to the Pitkin County Board of County Commissioners for their support
and adoption of this updated version of the Pitkin County Noxious Weed Management Plan.
Pitkin County Weed Management Plan
TABLE OF CONTENTS
6.32.010 Introduction
A. The Weed Problem
B. Enactment Authority
C. Plan Purpose and Objectives
D. How to Use this Plan
6.32.020 Definitions
6.32.030 Colorado Noxious Weed List
A. A, B, and C Listings
B. Colorado List A Noxious Weeds
C. Colorado List B Noxious Weeds
D. Colorado List C Noxious Weeds
6.32.040 Pitkin County Noxious Weed List
A. List A Weeds in Pitkin County
B. List B Weeds in Pitkin County
C. List C Weeds in Pitkin County
D. Declaration of Additional Noxious Weeds
6.32.050 Descriptions of Noxious Weeds in Pitkin County
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
M.
N.
O.
P.
Q.
R.
S.
T.
U.
V.
Section Overview
Absinth Wormwood
Bindweed, Field
Black Henbane
Brome, Downy ("Cheatgrass")
Burdock, Common
Caraway, Wild
Chamomile, Scentless
Chicory
Chinese Clematis
Cinquefoil, Sulfur
Dame's Rocket
Hemlock, Poison
Hoary Cress ("Whitetop")
Houndstongue
Knapweed, Diffuse
Knapweed, Meadow
Knapweed, Russian
Knapweed, Spotted
Mullein, Common
Oxeye Daisy
Pepperweed, Perennial
(Artemisia absinthium)
(Convolvulus arvensis)
(Hyoscyamus niger)
(Bromus tectorum)
(Arctium minus)
(Carum carvi)
(Matricaria perforata)
(Cichorium intybus)
(Clematis orientalis)
(Potentilla recta)
(Hesperis matronalis)
(Conium maculatum)
(Cardaria draba)
(Cynoglossum officinale)
(Centaurea diffusa)
(Centaurea pratensis)
(Acroptilon repens)
(Centaurea maculosa)
(Verbascum thapsus)
(Chrysanthemum leucanthemum)
(Lepidium latifolium)
W. Russian Olive
X. Salt Cedar
Y. Spurge, Cypress
Z. Spurge, Leafy
AA. Spurge, Myrtle
BB. Tansy, Common
CC. Thistle, Bull
DD. Thistle, Canada
EE. Thistle, Musk
FF. Thistle, Plumeless
GG. Thistle, Scotch
HH. Toadflax, Dalmatian
II. Toadflax, Yellow
(Elaeagnus angustifolia)
(Tamarix chinensis; T. ramosissima)
(Euphorbia cyparissias)
(Euphorbia esula)
(Euphorbia myrsinites)
(Tanacetum vulgare)
(Cirsium vulgare)
(Cirsium arvense)
(Carduus nutans)
(Carduus acanthoides)
(Onopordum acanthium, O. tauricum)
(Linaria genistifolia)
(Linaria vulgaris)
6.32.060 Pitkin County Weed Watch List
A. Why a Watch List?
B. Japanese Knotweed
C. Mediterranean Sage
D. Orange Hawkweed
E. Purple Loosestrife
F. Yellow Starthistle
6.32.070 Early Detection, Rapid Response
A. The EDRR Approach
B. Jurisdictional Overview of Pitkin County
1. Private Property
2. Municipalities
a. City of Aspen
b. Town of Snowmass Village
c. Town of Basalt
3. County Lands
a. Rights -of -Way
b. Airport
c. Solid Waste Center
d. Open Space and Trails
e. Grounds
4. State Lands
a. Colorado Department of Transportation
b. State Land Board
5. Federal Lands
a. White River National Forest
b. Bureau of Land Management
C. Cooperative Weed Management Areas
6.32.080 Enforcement
A. Statutory Enforcement Provisions Govern
B. Noxious Weeds Declared a Public Nuisance
C. Authorized Agents for Enforcement
D. Enforcement Flowchart
6.32.090 Priorities and Goals
A. Priorities
B. Goals
1. Short Term
2. Long Term
3. Figures
a. Sulfur Cinquefoil Containment Map
b. Hoary Cress Containment Map
c. Russian Knapweed Containment Map
d. Leafy Spurge Containment Map
6.32.100 Additional Requirements
Appendix
A. The Threat of Escaped Ornamentals
B. Native Thistles in Pitkin County
C. Landowner Weed Management Plan
D. Resource Directory
Chapter 6.32
NOXIOUS WEEDS
Sections:
6.32.010. Introduction
6.32.020. Definitions
6.32.030. Colorado Noxious Weed List
6.32.040. Pitkin County Noxious Weed List
6.32.050. Descriptions of Noxious Weeds in Pitkin County
6.32.060. Pitkin County Weed Watch List
6.32.070. Early Detection, Rapid Response
6.32.080. Enforcement
6.32.090. Priorities and Goals
6.32.100. Additional Rules, Regulations, and Policies
6.32.110. Prior Acts
Appendix
A. The Threat of Escaped Ornamentals
B. Native Thistles in Pitkin County
C. Landowner Weed Management Plan
D. Resource Directory
6.32.010. Introduction
A. The Weed Problem
The health of our environment is clearly a high priority for residents of Pitkin County and the
Roaring Fork Valley. Yet the health and productivity of our natural plant communities are
being threatened by the introduction of numerous invasive noxious weeds. These plants
displace native vegetation and important wildlife forage, disrupt native hydrology, alter soil
chemistry, and disturb the overall ecological balance of native habitats. They are also an
agricultural pest, crowding out desirable crops and requiring immense investments in time,
money, and materials to control. Thousands of acres of land in Pitkin County are already
infested with noxious weed species. Roadsides, ranchland, open space, housing
developments, industrial sites, private property, and Municipal, County, State, and Federal
lands are all affected.
In December 2001, the Colorado Department of Agriculture published Colorado's Strategic
Plan to Stop the Spread of Noxious Weeds. At that time, 1.5 to 2 million acres in Colorado
were infested with noxious/invasive weeds. In 2009, that number is probably even higher.
Such an increase in weed populations is a serious threat to the recreational, agricultural,
economic, and environmental value of land in Pitkin County and the region at large. For this
reason, the noxious weed problem is of concern not only to the rural and agricultural
community, but also to urban communities, small landowners, recreational land users, and
public land managers.
Noxious weeds have displaced at least 10% of Colorado's native plant species and have
severely degraded important native plant communities that provide essential habitat to more
than 85% of Colorado's wildlife species. This phenomenon is especially disturbing when it
comes to Colorado's delicate Riparian areas. While they compose less than 3% of the
Colorado landscape, these wetland areas along rivers and streams contain about 75% of
Colorado's plant and animal diversity, and play an important role in decreasing stream
sediment loads and controlling floodingl. Without a major integrated weed management
program, aggressive invasive plants will continue to infest and degrade the lands that we
value so highly.
B. Enactment Authority
In an effort to address the statewide threat of noxious weeds, the Colorado State Legislature
passed the Colorado Noxious Weed Act (C.R.S. 35-5.5-101 et seq.) ("The Act') and the
Rules Pertaining to the Administration and Enforcement of the Colorado Noxious Weed Act
(8 CCR 1206-2) ("The Rules").
The Act directs the Board of County Commissioners (BOCC) of each county in the Colorado
to adopt and administer a Noxious Weed Management Plan for all unincorporated land
within the county. It also directs the Board of County Commissioners to appoint a local
Weed Advisory Board (WAB), whose power and duties include:
• Development of a list of noxious weeds to be declared subject to integrated
management.
• Development of a recommended Weed Management Plan and management criteria
for noxious weeds within BOCC jurisdiction. This plan is to be reviewed and
amended at least once every three years.
• Recommendation to the BOCC that identified landowners be required to submit and
follow an integrated weed management plan for managing designated noxious weeds.
The BOCC has sole and final authority to approve, modify, or reject the management plan,
management criteria, management practice, and any other decision or recommendation of the
WAB.
C. Plan Purpose and Objectives
The Purpose of the Pitkin County Noxious Weed Management Plan (WMP) is to provide
guidelines for effectively managing Designated Noxious Weeds in Pitkin County.
The Objectives of this WMP are to:
• Comply with and execute the requirements of the Act and the Rules in Pitkin County.
• Institute regulations, guidelines, and policies within Pitkin County government that:
1 Environmental Protection Agency. "Wetlands in Region 8." EPA Home. 9 July 2009. WCMS. 6 November
2009. http://www.epa.gov/region8/water/wetlands/wetr8.html.
o emphasize and support prevention of noxious weed infestation,
o improve communication on noxious weed issues, and
o allow for swift and effective enforcement of the WMP, the Act, and the
Rules in Pitkin County.
• Institute County -wide programs that address the following fundamentals:
o Awareness, Education, and Training
o Prevention; Early Detection and Rapid Response
o Inventory, Survey, and Mapping
o Integrated Management (Biological, Chemical, Cultural, and Mechanical)
o Monitoring and Evaluation
o Reporting
• Foster a spirit of cooperation among landowners (be they Federal, State, County,
Municipal, or private) to carry out regional Integrated Management Plans.
• Serve as an educational tool for the public: as a guide to the weeds in Pitkin County
and as a manual for landowners working to control weeds on their own property.
D. How to use this Plan
The Pitkin County Noxious Weed Management Plan (WMP) is an official legal document,
adopted as an Ordinance by the Board of County Commissioners. As such, this WMP is the
primary policy guiding the weed management operations and enforcement activities of the
Pitkin County Land Management program.
However, this WMP is also intended for use by the public as an educational tool and weed
control manual. Chapters 2-5 provide a wealth of information to the public on how to
identify and control noxious weeds in Pitkin County. In addition, Chapter 6 provides
information on who to contact when reporting a new or suspicious weed infestation.
Use the following table to guide you the right section of the WMP to answer your questions:
If you want to know...
see...
...what weeds are designated "Noxious" in Colorado...
...what the A, B, and C Listings mean...
...Section 2:
Colorado
Noxious Weed List
...which Noxious Weeds are found in Pitkin County...
...Section 3:
Pitkin County
Noxious Weed List
...the name of a weed you have...
...how to identify a specific weed...
...common look-alikes of a specific weed...
...how to control a specific weed...
...common locations of a weed in Pitkin County...
...Section 4:
Descriptions of Noxious Weeds in
Pitkin County
...Section 5:
Pitkin County
...what weeds may soon be coming to Pitkin County...
...which weeds are the most important to report...
Weed Watch List
and
Section 2:
Colorado Noxious Weed List
(any List A weed)
...what to do if you find a new weed...
...who to contact about a weed problem...
...the jurisdiction of agencies in Pitkin County...
...Section 6:
Early Detection,
Rapid Response
and
Appendix D:
Resource Directory
...how Pitkin County enforces the Act and the Rules...
...Section 7:
Enforcement
...why Noxious Weeds are such a big deal...
...why you should know how to identify noxious weeds...
...why you should landscape with native plants...
...Appendix A:
The Threat of Escaped
Ornamentals
...about Native Thistles in Colorado...
...how to distinguish Native and Noxious Thistles...
Appendix B:
Native Thistles in Pitkin County
...the meaning of a word or term used in this WMP...
...Appendix E:
Definitions
...how to calibrate your spray equipment...
...how to determine how much herbicide to use...
...how to read an herbicide label...
Pitkin County Land Manager
970-920-5214
www.aspenpitkin.com/weeds
6.32.02 Definitions
The Act Colorado Noxious Weed Act, C.R.S. 35-5.5-101 et seq.
Adjacent
Having a common boundary that meets or touches at some point.
Aggressive Fast growing, tending to propagate and spread quickly.
Agriculture
keeping of
Alien Plant
Annual
Best
Management
Practices
Biennial
Biological
Management
Bolt
BOCC
Bract
Browse
CDA
Uses involving the cultivation of land, production of crops, and/or the
livestock and the preparation of these products for man's use and disposal.
A plant species that is not indigenous to the state of Colorado
A plant which, having germinated, completes its life cycle in one year
The most efficient (least amount of effort) and effective (best results) way
of accomplishing a task, based on repeatable procedures that have proven
themselves over time for large numbers of people.
A plant which, having germinated, takes two years to complete its life
cycle. The first year it typically lives only in a vegetative form, such as a
rosette of leaves. The second year the plant grows a flowering shoot, sets
seed, and dies.
The use of organisms to disrupt the growth of noxious weeds
To develop a flowering stem from a rosette.
Board of County Commissioners
A reduced or modified leaf often surrounding the base of a flower
Tender shoots, twigs, and leaves of trees and shrubs fit for food for
wildlife
Colorado Department of Agriculture
Chemical
Management The use of herbicides or plant growth regulators to disrupt the growth of
noxious weeds.
The
Commissioner
Containment
Cooperative
Weed Mgmt.
Area
County
Cultural
Management
The Commissioner of the Department of Agriculture or his or her
designee.
Maintaining an intensively managed buffer zone that separates infested
regions, where suppression activities prevail, from largely un-infested
regions, where eradication activities prevail.
A partnership of Federal, State, and Local government agencies, tribes,
individuals, and various interested groups that manage noxious weeds or
invasive plants in a defined area.
The unincorporated areas of Pitkin County
Methodologies or management practices that favor the growth of desirable
plants over noxious weeds, including maintaining an optimum fertility and
plant moisture status in an area, planting at optimum density and spatial
arrangement in an area, and planting species most suited to an area.
Designated
Noxious Weed A non-native, invasive plant or plant parts identified as a threat to native
plant communities and included on the Colorado or Pitkin County
Noxious Weed lists.
Desirable
Plants
Eradication
Escaped
Ornamental
Exotic Plant
Forage
Plants considered to be advantageous and beneficial to environmental
viability.
Reducing the reproductive success of a noxious weed species or specified
noxious weed population in largely un-infested regions to zero and
permanently eliminating the species or population with a specified period
of time. Once all specified weed populations are eliminated or prevented
from reproducing, intensive efforts continue until the existing seed bank is
exhausted.
A plant originally intended for horticultural or landscape situations that
has escaped its intended boundaries.
A plant that is not a native member of the native or natural community in
which it is found.
Plant material (mainly plant leaves and stems) eaten by animals.
Glyphosate
Herbaceous
Infestation
Integrated
Management
Invasive
Invasive
Ornamental
Involucre
Landowner
Lobe
Local
Governing
Body
Local
Non -selective active ingredient of herbicides such as Round -Up.
A non -woody plant that dies to the ground each year.
The presence of a large number of pest organisms in an area.
The planning and implementation of a coordinated program utilizing a
variety of methods for managing noxious weeds, the purpose of which is
to achieve specified management objectives and promote desirable plant
communities. Such methods may include, but are not limited to:
education, preventative measures, good stewardship, and Biological,
Chemical, Cultural, and Mechanical Management.
Integrated Pest Management has been further defined as: a decision
support system for the selection and use of pest control tactics, singly or
harmoniously coordinated into a management strategy, based on
cost/benefit analysis that takes into account the interests of and impacts on
producers, society, and the environment. (Marcos Kogan. 1998. Integrated
Pest Management: Historical Perspectives and Contemporary
Developments. Annual Review of Entomology. 43:243-270.)
Capable of entering a native plant community to the detriment of native
species.
A plant originally intended for horticultural or landscape situations that
has escaped its intended boundaries and is capable of invading a plant
community and creating a monoculture.
A cluster of bracts surrounding the base of an inflorescence
Any owner of record of federal, tribal, state, county, municipal, or private
land.
A part into which a leaf is divided.
The Board of County Commissioners of a county, the City Council of a
city and county or statutory or home rule city, the Board of Trustees of a
statutory town or home rule town, or the Board of Selectmen or City
Council of a territorial charter municipality, as the context so requires.
Noxious
Weed
Management
Management
Objective
Any plant of local importance that has been declared a noxious weed by
the local governing body.
Any activity that prevents a plant from establishing, reproducing, or
dispersing itself.
Means the specific, desired result of integrated management efforts and
includes Eradication, Containment, Suppression, and Restoration.
Management
Plan The noxious weed management plan developed by any person or the local
advisory board using integrated management.
Mechanical
Management
Monocarpic
Perennial
Monoculture
Native Plant
Neighboring
Using methodologies or management practices that physically disrupt
plant growth, including tilling, mowing, burning, flooding, mulching,
hand -pulling, hoeing, and grazing.
A perennial plant which flowers and bears fruit only once.
A single homogeneous stand of plants without diversity or dissension.
A plant species that is indigenous to the state of Colorado.
Any property located within a half -mile radius of the boundary of a
subject property
Noxious Weed An alien plant or parts of an alien plant that has been designated by rule as
being noxious or has been declared a noxious weed by a local advisory
board, and meets one or more of the following criteria:
1. Aggressively invades or is detrimental to economic crops or native
plant communities;
2. Is poisonous to livestock;
3. Is a carrier of detrimental insects, diseases, or parasites;
4. The direct or indirect effect of the presence of this plant is
detrimental to the environmentally sound management of natural
or agricultural ecosystems.
Noxious
Weed
Management
The planning and implementation of an integrated program to manage
noxious weed species
Ornamental
Perennial
Petiole
Pinnate
A decorative, non-native plant often sold through nurseries or spread
through seed collection. Many ornamental plants can become a threat to
native plant species, growing aggressively and without natural predators,
and thus out -competing the plants of the natural ecosystem.
A plant that grows for three years or more. Usually flowering and producing
fruit each year. The above ground part of the plant may die, but new
growth comes from the roots or the crown each spring.
Plant Growth
Regulator
Restoration
Rhizome
Rosette
The Rules
Sessile
Silique
State Noxious
Weed
A small stalk attaching the leaf blade to the stem.
In the form of a feather
A substance used for controlling or modifying plant growth processes
without appreciable phytotoxic effect at the dosage applied.
Removal of noxious weed species and reestablishment of desirable plant
communities on lands of significant environmental or agricultural value in
order to help restore said value.
An elongated subterranean plant stem that produces shoots above and
roots below, and is distinguished from a true root in possessing buds,
nodes, and scale -like leaves.
A cluster of leaves growing in crowded circles from a common center or
crown, usually at or close to the ground.
Rules Pertaining to the Administration and Enforcement of the Colorado
Noxious Weed Act (8 CCR 1206-2)
Without a petiole, pedicel, or stalk, (i.e. directly attached)
Narrow, elongated seed pod characteristic of the Mustard family.
Any noxious weed identified by the commissioner by rule after notifying
and consulting with the State Noxious Weed Advisory Committee created
by C.R.S. 35-5.5-108.7
State Weed
Coordinator The State Weed Coordinator under contract with or appointed by the
Commissioner pursuant to C.R.S. 35-5.5-117.
Suppression Reducing the vigor of noxious weed populations within an infested region,
decreasing the propensity of noxious weed species to spread to
surrounding lands, and mitigating the negative effects of noxious weed
populations on infested lands. Suppression efforts may employ a wide
variety of integrated management techniques.
Surfactant A compound that improves the emulsifying, dispersing, spreading,
wetting, or other surface modifying properties of liquids. Used with an
herbicide, a surfactant aids in adhesion of the herbicide to foliage and its
absorption by the plant.
Umbel
WAB
An umbrella -shaped flower -head in which the individual flowers are borne
on short stems arising from the top of a main stem. This is the
inflorescence typical of the parsley family (e.g. plants like carrot, dill, and
fennel).
The Pitkin County Weed Advisory Board, created and appointed pursuant
to C.R.S. 35-5.5-107. This group of individuals is appointed by the Board
of County Commissioners to advise on matters of noxious weed
management.
Weed Any undesirable plant.
Wildflower The flower of a wild or uncultivated plant.
6.32.020. Colorado Noxious Weed List
A. A, B, and C Listings
The State of Colorado has designated 73 plants as Noxious Weeds, and has categorized them
into three lists based on priority for management in Colorado. These lists have been named
Lists A, B, and C. Most simply put:
• List A plants are newly arrived and/or less common in Colorado and must be
eradicated from all lands in the State.
• List B includes plants whose continued spread in Colorado should be halted.
• List C plants are those for which local governments have authority to decide the
management strategy.
The purpose of such categorization is to guide the State and local governments in developing
Management Strategies for each weed. The Management Strategy of a particular weed in an
area may be one of the following (see Appendix E for more complete definitions):
• Eradication (complete elimination of all populations of a weed)
• Containment (confinement of populations of a weed to a defined area)
• Suppression (attempt to limit the vigor and spread of populations within a region)
All List A species have been designated by the Colorado Commissioner of Agriculture ("the
Commissioner") for eradication. This means that it is a violation to allow any List A species
to produce seed or develop other reproductive means such as roots, shoots and runners.
Many List A weeds are not yet present in Colorado, but have become a problem in
neighboring states. Others are present in small isolated populations. It is the intent of the
Commission to eliminate these species before they become widespread. The Rules allow the
local governing authority to file for a compliance waiver if it is determined that eradication is
not a practical management objective for specific populations.
List B weed species may be designated for eradication, suppression, or containment,
depending on the extent of their presence in a particular county. The local Management
Strategy for each List B species in each county is determined by the Commissioner (in
consultation with the State Noxious Weed Advisory Committee, local governments, and
other interested parties). From these local Management Strategies, the Commissioner
develops a State-wide noxious weed management plan for each List B species. This Plan is
designed to stop the continued spread of List B species, making it a violation to allow any
List B species to spread into any un-infested area.
Local governments are left to decide whether to require management of List C weed species,
and, if so, whether the Management Strategy will be Eradication, Containment, or
Suppression. State Management Plans for List C weed species developed by the
Commissioner are designed to support the weed management efforts of local governing
bodies. The goal of such plans is not to stop the continued spread of these species. Rather,
they are meant to provide additional education, research, and biological control resources to
jurisdictions that choose to require management of List C species.
B. Colorado List A Noxious Weeds
African rue (Peganum harmala)
Camelthorn (Alhagi pseudalhagi)
Common crupina (Crupina vulgaris)
Cypress spurge (Euphorbia cyparissias)
Dyer's woad (Isatis tinctoria)
Giant salvinia (Salvinia molesta)
Hydrilla (Hydrilla verticillata)
Meadow knapweed (Centaurea pratensis)
Mediterranean sage (Salvia aethiopis)
C. Colorado List B Noxious Weeds
Absinth wormwood (Artemisia absinthium)
Black henbane (Hyoscyamus niger)
Bouncingbet (Saponaria officinalis)
Bull thistle (Cirsium vulgare)
Canada thistle (Cirsium arvense)
Chinese clematis (Clematis orientalis)
Common Buckthorn (Rhamnus cathartica)
Common Tansy (Tanacetum vulgare)
Common Teasel (Dipsacus fullonum)
Corn Chamomile (Anthemis arvensis)
Cutleaf teasel (Dipsacus laciniatus)
Dalmatian toadflax (Linaria dalmatica)
Dalmatian toadflax (Linaria genistifolia)
Dame's rocket (Hesperis matronalis)
Diffuse knapweed (Centaurea diffusa)
Eurasian watermilfoil (Myriophyllum spicatum)
Glossy Buckthorn (Rhamnus frangula)
Hoary cress (Cardaria draba)
Houndstongue (Cynoglossum officinale)
Leafy spurge (Euphorbia esula)
Mayweed chamomile (Anthemis cotula)
D. Colorado List C Noxious Weeds
Chicory (Cichorium intybus)
Common burdock (Arctium minus)
Common mullein (Verbascum thapsus)
Downy brome (Bromus tectorum)
Field bindweed (Convolvulus arvensis)
Halogeton (Halogeton glomeratus)
Johnsongrass (Sorghum halepense)
Medusahead (Taeniatherum caput-medusae)
Myrtle spurge (Euphorbia myrsinites)
Orange Hawkweed (Hieracium aurantiacum)
Purple loosestrife (Lythrum salicaria)
Rush skeltonweed (Chondrilla juncea)
Sericea lespedeza (Lespedeza cuneata)
Squarrose knapweed Centaurea virgata)
Tansy ragwort (Senecio jacobaea)
Yellow starthistle (Centaurea solstitialis)
Moth mullein (Verbascum blattaria)
Musk thistle (Carduus nutans)
Oxeye daisy (Chrysanthemum leucanthemum)
Perennial pepperweed (Lepidium latifolium)
Plumeless thistle (Carduus acanthoides)
Quackgrass (Elytrigia repens)
Redstem filaree (Erodium cicutarium)
Russian knapweed (Acroptilon repens)
Russian olive (Elaeagnus angustifolia)
Salt cedar (Tamarix ramosissima)
Scentless chamomile (Matricaria perforata)
Scotch thistle (Onopordum acanthium)
Scotch thistle (Onopordum tauricum)
Spotted knapweed (Centaurea maculosa)
Spurred anoda (Anoda cristata)
Sulfur cinquefoil (Potentilla recta)
Tatarian Honeysuckle (Lonicera Tatarica)
Venice mallow (Hibiscus trionum)
Wild caraway (Carum carvi)
Yellow nutsedge (Cyperus esculentus)
Yellow toadflax (Linaria vulgaris)
Jointed goatgrass (Aegilops cylindrica)
Perennial sowthistle (Sonchus arvensis)
Poison hemlock (Conium maculatum)
Puncture Vine (Tribulus terrestris)
Velvetleaf (Abutilon theophrasti)
Wild proso millet (Panicum miliaceum)
6.32.040. Pitkin County Noxious Weed List
A. List A Noxious Weeds in Pitkin County
The following List A Noxious Weeds are designated for Eradication from Pitkin County:
• Cypress Spurge (Euphorbia cyparissias)
• Meadow Knapweed (Centaurea pratensis)
• Myrtle Spurge (Euphorbia myrsinites)
B. List B Noxious Weeds in Pitkin County
The Pitkin County WAB shall establish management recommendations for List B weed
species in Pitkin County for which the Commissioner has not developed and implemented
management plans. These recommendations shall be submitted to the BOCC for adoption.
Once adopted, management objectives for List B noxious weed species will be
communicated to the Commissioner.
The following List B Noxious Weeds are designated for Eradication from Pitkin County:
• Absinth wormwood (Artemisia absinthium)
• Black henbane (Hyoscyamus niger)
• Bull thistle (Cirsium vulgare)
• Chinese clematis (Clematis orientalis)
• Dalmatian toadflax (Linaria dalmatica)
• Dame's rocket (Hesperis matronalis)
• Diffuse knapweed (Centaurea diffusa)
• Plumeless thistle (Carduus acanthoides)
• Russian knapweed (Centaurea repens)
• Salt cedar (Tamarix chinensis)
• Salt cedar (Tamarix ramosissima)
• Spotted knapweed (Centaurea maculosa)
The following List B Noxious Weeds are designated for Containment in Pitkin County:
• Oxeye daisy (Chrysanthemum leucanthemum)
• Russian olive (Elaeagnus angustifolia)
• Scotch thistle (Onopordum acanthium)
• Sulfur Cinquefoil (Potentilla recta)
The following List B Noxious Weeds are designated for Suppression in Pitkin County:
• Canada thistle (Cirsium arvense)
• Common tansy (Tanacetum vulgare)
• Hoary cress (Cardaria draba)
• Houndstongue (Cynoglossum officinale)
• Leafy spurge (Euphorbia esula)
• Musk thistle (Carduus nutans)
• Perennial pepperweed (Lepidium latifolium)
• Scentless chamomile (Matricaria perforata)
• Wild caraway (Carum carvi)
• Yellow toadflax (Linaria vulgaris)
C. List C Noxious Weeds in Pitkin County
The Pitkin County WAB shall establish management recommendations for List C weed
species in Pitkin County. These recommendations shall be submitted to the BOCC for
adoption. Once adopted, management objectives for List C noxious weed species will be
communicated to the Commissioner.
The following List C Noxious Weeds are designated for Eradication from Pitkin County:
• Chicory (Cichorium intybus)
The following List C Noxious Weeds are designated for Suppression in Pitkin County:
• Common burdock (Articum minus)
• Common mullein (Verbascum thapsus l)
• Downy brome (Bromus tectorum)
• Field bindweed (Convolvulus arvensis)
• Poison hemlock (Conium maculatum)
D. Declaration of Additional Noxious Weeds
The BOCC may declare additional noxious weeds within its jurisdictional boundaries after a
public hearing with thirty days prior notice to the public. Any declaration of additional
noxious weeds shall include management objectives, per The Act § 35-5.5-108. The
integrated management of any additionally declared noxious weed species shall be the
responsibility of the landowner, as required by The Act and The Rules.
6.32.050 Descriptions of Noxious Weeds in Pitkin County
A. Section Overview
The purpose of this section is to provide the public with a practical guide to the identifica-
tion and management of Designated Noxious Weed Species in Pitkin County. Photographs
and the following information are provided for each plant on the Pitkin County Noxious
Weed List:
*Key Characteristics, including plant family, area of origin, identifying characteristics,
mode(s) of reproduction, and (where applicable) toxicity.
•Locations of both major and new infestations in Pitkin County
*Best Management Practices based on the Colorado Commissioner of Agriculture's
prescribed management plans. These practices include Biological, Cultural, Mechani-
cal, and Chemical Control methods. Because there are many factors involved in choos-
ing and executing an appropriate chemical treatment method, no specific herbicide and
application rate information is included here. Contact the Land Management depart-
ment directly to learn more about chemical treatment options appropriate for the site and
weeds in question.
•Look-Alikes Some of our noxious weeds are commonly confused with native or com-
mon non-native (but non -noxious) weeds. Where applicable, common look-alikes are
pictured and distinguished from the noxious weed.
This section is intended to be a first -reference, not an exhaustive outline. Appendix D: Re-
source Directory lists a variety of websites that provide more information about Noxious
Weeds. The Pitkin County Land Management department is also available to answer any
further questions.
B. Absinth Wormwood
(Artemisia absinthium)
Key Characteristics:
Absinth wormwood is a member of the
Sunflower family. Absinth Wormwood
is a long-lived perennial with a strong
aromatic odor, bitter taste, and a shrub -
like appearance. Often misidentified as
native Artemisia species, Absinth
Wormwood is often overlooked, making
good identification skills key to effec-
tive prevention and control.
Plants are multiple -stemmed, grow 16
to 48 inches tall, and die back every
winter to crowns at soil -level. (In comparison, our native Big Sagebrush (A. tridentata) has one
main stem that branches, and it retains its leaves all year.)
Leaves consist of rounded lobes, 3-10 cm wide by nearly as long, that are divided many times.
Leaves are alternate, with lower leaves on long petioles and upper leaves on short petioles and less
lobed. This contrasts to native Fringed Sage (A. frigi da) whose
leaves are smaller, much more thinly divided, and almost lace -like
throughout. In addition, Absinth Wormwood leaves are a bluer,
olive gray -green color than native Artemisia species.
Locations:
Known infestations in Pitkin County exist in the AABC and North
Forty neighborhoods, on Red Mountain, in Snowmass Village and
Old Town Basalt, along Maroon Creek, Brush Creek, Capitol
Creek, and Thompson Creek Roads, and along Hwy 133 near the
Garfield-Pitkin County Line and near Marble.
Biological control:
No known biological controls at this time.
Cultural control:
Good perennial grass growth resists infestation. Be aware that varieties of Absinth Wormwood may
be sold as ornamentals at garden shops and may be a contaminant in native sage seed mixes. Pur-
chase only certified -weed free seed.
Mechanical control:
Summer fallow and fall tillage prevent establishment on cultivated land, but spring tillage is less
effective. Cutting or mowing reduces seed production, but will not kill root system.
Chemical control:
There are effective herbicide options for Absinth Wormwood control. Contact the Pitkin County
Land Management Department for more specific information about products, rates, and equipment
calibration.
B. Absinth Wormwood (Artemisia absinthium) (continued)
Native Look-Alikes: Absinth Wormwood is closely related to several of our native sage species.
These plants are shown side -by -side below for comparison.
Absinth Wormwood
(A. absinthium)
Photo courtesy of Lisa Tasker,
Prairie Sage
(A. ludoviciana)
E.M. Ecological, LLC
Mountain Big Fringed Sage
Sagebrush (A. frigida)
Prairie Sage
(A. ludoviciana)
Big Mountain Sagebrush
(A. tridentata)
Fringed Sage
(A. frigida)
C. Field Bindweed
(Convolvulus arvensis)
Kev Characteristics:
Field bindweed is a member of the Morning-glory family,
introduced from Europe. It is a creeping perennial that
reproduces by both seed and rhizomes.
Stems lie close to the ground, are smooth, slender, slightly
angled, 1 to 4 feet long, and spread thickly over the ground
or wind around erect plants or other objects.
Leaves are alternate, 1 to 2 inches long with great varia-
tion in shape. They are somewhat arrow shaped with
spreading, pointed, or blunt lobes at the base. The flowers
are white or pink bell shaped about 3/4 to 1 inch broad.
Field bindweed is one of the most competitive perennial weeds in Colorado, and is very common
throughout Pitkin County. A two or three year food supply is stored in the root system, making
this plant very difficult to kill. It is best to eliminate young bindweed plants before they have a
chance to develop their extensive root system. Seeds can stay viable in the soil for up to 40 years.
This plant is also poisonous to horses.
Biological control:
The Field Bindweed Gall Mite, Aceria malherbae, is now available for Bindweed Control. It is
available for a small fee from the Colorado Depth talent of Agriculture Insectary until 2012, when
distribution will be turned over to counties to manage.
Cultural control:
Good vegetative cover helps but does not prevent Field Bindweed invasion and spread.
Mechanical control:
Do not Cultivate! Cultivation will chop up the root system and spread it more rapidly. Smothering
or clipping (without disturbing roots) can be effective on small infestations if done thoroughly.
Chemical control:
There are effective herbicide options for Field Bindweed control. Contact the Pitkin County Land
Management Depai tiuent for more specific information about products, rates, and equipment cali-
bration.
D. Black Henbane
(Hyoscyamus niger)
Key Characteristics:
Black henbane, a member of the nightshade
family, was introduced from Europe as an orna-
mental and medicinal herb. Blooming June
through September this weed may be an annual
or biennial and grows from 1 to 3 feet tall.
Leaves are shallowly -lobed to coarsely -toothed
and have sticky hairs. Flowers are brownish -
yellow with a purple center and purple veins and
have a foul odor. Fruits are about 1 inch long
with 5 lobes. Black Henbane is poisonous to
both livestock and humans.
Locations:
This plant is relatively rare in Pitkin County,
with most outbreaks happening in areas where
heavy earth -moving has occurred. Black hen-
bane plants have been identified on Brush Creek
Road, near the Aspen Recreation Center, along
Hwy 82 near the Maroon Creek Bridge, and at
the Pitkin County Airport.
Biological control:
No known biological controls at this time.
Cultural control:
Good vegetative cover substantially reduces chance of infestation. Beware of potentially contami-
nated fill, dirt, or hay. Avoid overgrazing, as this weed is a common invader of overused pasture.
Mechanical control:
Hand pull or dig from moist soil, to remove the entire taproot system. Be sure to bag plants that
have been removed during or after flowering to prevent potential seed spread.
Chemical control:
There are effective herbicide options for Black Henbane control. Contact the Pitkin County Land
Management Depai Invent for more specific information about products, rates, and equipment cali-
bration.
E. Downy Brome ("Cheatgrass")
(Bromus tectorum)
Key Characteristics:
Downy Brome or "cheatgrass" is a grass introduced from
Eurasia. Reproduction is by seed. Plants are 4-30 inches
tall and blades densely covered with soft hairs, giving
them a downy feel. Flowers in mid -spring are followed by
seedheads 2-6 inches long and usually purplish at matur-
ity. Cheatgrass competes with more desirable perennial
grasses for moisture because of its early spring emergence.
Once mature, the dry plant is a nuisance and fire hazard.
Downy Brome seeds can germinate in the fall, winter, and
spring. Most seeds germinate within one year of matura-
tion. Frequent late summer or late fall rains will cause rapid
germination and abundant fall growth. However, if adequate fall moisture
Brome can act like a spring annual.
is not available, Downy
Locations:
This plant is located throughout Pitkin County, especially along roadsides and in areas where
heavy disturbance has occurred.
Biological control:
Scientists are working on specific bacteria for biological control but still in testing stage.
Cultural control:
Seeding with aggressive, native, perennial grasses can help compete against Downy Brome.
Maintain range and pasture in good condition. Promote healthy grass growth through proper irri-
gation and fertilization. Do not overgraze.
Mechanical control:
Early spring tillage of fallow ground, tillage prior to planting spring -season crops, and tillage op-
erations that bury downy brome seeds (mold -board plowing) are effective mechanical methods.
Neither mowing nor burning are effective controls to prevent seed spread.
Chemical control:
There are effective herbicide options for Cheatgrass control. Contact the Pitkin County Land
Management Depai Intent for more specific information about products, rates, and equipment cali-
bration.
F. Common Burdock
(Arctium minus)
Key Characteristics:
Common burdock is a member of the
Sunflower family. It is an introduced
biennial which reproduces by seed in its
second year. In the first year of growth
the plant forms a rosette; the second
year the plant bolts and flowers. Bur-
dock can grow up to 6 feet tall, has
enormous leaves and prickly burs. The
flowers are purple and white on numer-
ous heads. Burdock grows along road-
sides, ditch banks, and in neglected ar-
eas.
Locations:
This plant is a very serious threat to
sheep as the burs can significantly dam-
age the quality of their wool. Common
burdock is found throughout Pitkin
County.
Biological control:
None known at this time.
Cultural control:
Prevent the establishment of new infestations by
minimizing disturbances and seed dispersal, eliminat•
-
ing seed production and maintaining healthy native plant communities.
Mechanical control:
Burdock will not stand repeated cultivation, cutting, digging or pulling. Mechanical control is labori-
ous but effective; properly bag and dispose of mature burs.
Chemical control:
There are effective herbicide options for Common Burdock control. Contact the Pitkin County Land
Management Depai linent for more specific information about products, rates, and equipment cali-
bration.
G. Wild Caraway
(Carum carvi)
Key Characteristics:
Wild caraway is a member of the Parsley family It is
a biennial plant, producing a low -growing rosette of
leaves in its first year of growth, and then a flowering
stalk (bolt) in the second year. The plant is supported
by a narrow taproot and grows in a wide range of
soil types. Bolting plants can tolerate some spring
flooding and seedlings can survive light frost. Stems
are erect, smooth, branched, usually hollow, and
grow 1- 3 feet tall. There can be several stems per
plant. Leaves are alternate and very finely divided
(parsley -like). The leaves of the first -year rosettes
can look very similar to yarrow, a native plant. The
flowers of Wild Caraway are usually white, but occa-
sionally pinkish, and occur in loose umbels. Fruit
has a distinct caraway odor.
Locations:
Wild caraway is grown in Canada as a spice crop;
however it has escaped cultivation and has been invading pastures,
rangeland and natural areas for several years now. This plant is prolific
in Pitkin County. Small infestations have been noticed in Maroon Bells
Park.
Biological control:
None known at this time.
Cultural control:
Healthy, competitive vegetation helps protect areas from invasion.
Mechanical control:
Hand -pulling of bolting stalks is effective at preventing seed production,
but at maturity the seed heads are extremely fragile and shatter easily.
At this stage a plastic bag can be carefully placed over the mature plant, and closed tightly around
the stem while hand -pulling. Carefully done, this method can remove seed without accidentally
spreading it. Collected seed should be disposed of in landfill -bound garbage or thoroughly burned.
Mowing is not effective because the plants will stay short and bloom.
Chemical control:
There are effective herbicide options for Wild Caraway control. Contact the Pitkin County Land
Management Department for more specific information about products, rates, and equipment cali-
bration.
Yarrow
(Achillea lanulosa)
Smaller and shorter, leaves more finely divided
than Wild Caraway; stem and leaves wooly;
seeds lack caraway odor
G. Wild Caraway (Carum carvi) (continued)
Native Look-Alikes: Examples of similar -looking natives are pictured below. Contact the Land
Management office with further questions.
Cow Parsnip
(Heracleum sphondylium)
Stem thicker, leaves much larger and less subdivided
than Wild Caraway; seeds lack caraway odor.
Porter's Loveage/Osha
(Ligusticum porters)
Leaves not as finely divided as Wild Caraway;
seeds lack caraway odor.
H. Scentless Chamomile
(Matricaria perforata)
Key Characteristics:
Scentless chamomile is a member of
the Sunflower family. It is an annual
that grows 1/2 to 2 feet tall with a
bushy habit. Blossoms are showy
with white ray (outer) flowers and
yellow centers. Leaves are fern -like.
Seeds are viable as soon as the flower
is formed, and remain so up to 15
years when buried, making early con-
trol of
Scentless Chamomile the key to effec-
tive management.
This weed is nearly identical in appearance to the strongly -scented species used for tea, but lacks
the distinctive chamomile odor. It has no forage value, and can in fact cause skin rashes and blis-
tering of mucus membranes, sometimes resulting in the ultimate starvation of wildlife who have
attempted to eat it.
Locations:
Scentless Chamomile is common along
rights -of -way and ditches and in culti-
vated fields and disturbed sites through-
out Pitkin County. It is a typical front-
line invader in areas of heavy distur-
bance.
Biological control:
None known at this time.
Cultural control:
Promptly re -seed disturbed areas with
competitive native grasses.
Mechanical control:
Hand pulling is the most effective
method to both control Scentless
Chamomile populations and prevent
their spread into new areas. Once plants
are pulled, they should be bagged and
trashed if any flowers are present, as
they likely contain viable seed.
H. Scentless Chamomile (Matricaria perforata) (continued)
Chemical control:
There are effective herbicide options for Scentless Chamomile control. The earlier the application
the more effective the control. Herbicide application is not effective on Scentless Chamomile when
the majority of the plants are flowering because seed production has already occurred. Contact the
Pitkin County Land Management Department for more specific information about products, rates,
and equipment calibration.
Native Look-Alikes:
Foliage and Growth Habit are the keys to distinguishing Scentless Chamomile from white native
daisies in Colorado. Stands of Chamomile have a distinctive bushy appearance, and the foliage is
very finely divided and fern -like. By contrast, the native white daisies that most closely resembling
Scentless Chamomile (e.g., species of Erigeron like that pictured below) usually occur small clumps
and have leaves that are entire or slightly lobed.
Whiplash Daisy
(Erigeron flagellaris)
Note that while the blossom is similar to that of Scentless Chamomile,
leaves are basal and entire (left), and stands are not bushy (right).
I. Chicory
(Cichorium intubus L)
Key Characteristics:
Chicory is a member of the Sunflower family. It is native
to the Mediterranean region, but now broadly distributed
throughout the northern hemisphere. Chicory is a tap -
rooted perennial that grows 1-6 feet tall and . Low -
growing rosette leaves resemble dandelion leaves but
have fine hairs. Blue flowers (occasionally pink or white)
usually close by midday. Leaves are often used in salads
and dried roots as a coffee substitute.
Locations:
Patches of Chicory exist along Hwy 133 near the Penny
Hot Springs, and along Capitol Creek and
Sopris Creek roads.
Biological control:
None known at this time.
Cultural control:
This perennial weed is difficult to eliminate. Prevent inva-
sion by minimizing soil disturbance and use of contami-
nated seed, eliminating seed production by current infesta-
tions, and maintaining healthy native plant communities.
Mechanical control:
Chicory may be controlled by mowing, cutting, or pulling
plants before seed production. This process may have to be
repeated annually to exhaust nutrient reserves in the roots ',e r
of the plants as well as to eliminate plants that emerge from
the soil seed bank.
Chemical control:
There are effective herbicide options for Chicory control.
Best control occurs when the plants are actively growing,
and in the fall to rosettes. Contact the Pitkin County Land
Management Department for more specific information about products,
rates, and equipment calibration.
J. Chinese Clematis
(Clematis orientalis)
Key Characteristics:
Chinese clematis is a member of the Buttercup family. It
is an herbaceous to woody perennial vine, initially in-
troduced as an ornamental. Stems reach 10-15 ft, with
gray -brown bark, and tend to climb on rocks, fences,
bushes, and trees. Roots are 5-10 ft long. Leaves are
opposite and may be in groups of three. Each large soli-
tary yellow flower produces numerous feathery, long-
tailed seeds which are conspicuous all winter.
Locations:
Chinese clematis stands can be found in the Town of
Snowmass Village. It is also present in Garfield County
near No Name. There are many native clematis species in
Colorado, all having white flowers.
Biological control:
None known at this time.
Cultural control:
The only recommendation available for preventing the spread of this species is by eliminating seed
production from established stands, and discontinuing its use as an ornamental.
Mechanical control:
Hand pull woody vine before seed heads mature.
Chemical control:
Contact the Pitkin County Land Management Department for more specific information about herbi-
cide products, application rates, and equipment calibration.
Look-Alikes:
There are many native Clematis species in Colorado. Western Vir-
gin's Bower Clematis ligusticifolia) is a common example because its
leaves are very similar to Chinese Clematis, but it can be distinguished
by its flowers which are smaller, white and occur in clusters rather
than solitary on stems.
Other native Clematis species
include Blue Clematis (Clematis
occidentalis), and Rocky Moun-
tain clematis (Clematis columbi-
ana), both of which have light
blue -lavender flowers.
Western Virgin's Bower
(Clematis ligusticifolia)
1 Blue Clematis
(Clematis occidentalis)
K. Sulfur Cinquefoil
(Potentilla recta)
Key Characteristics:
Sulfur Cinquefoil is a member of the Rose family. It is
a long-lived, tap -rooted perennial that grows upright to
1-2 ft tall, with hairy stems. Flowers are light -yellow
in color with a dark yellow center and 5 petals. Leaves
are palmate and divided into about five saw-toothed
leaflets.
Locations:
Although not a new discovery in Pitkin County (it's been
around at least eight years) Sulfur Cinquefoil is new to
the Pitkin County Weed List. Small patches
have been found at the Pitkin County Airport
and east of Aspen around North Star, in Woody
Creek near Jaffee Park, on the Child Ranch on
Capitol Creek Road, up the Frying Pan, and in
the Crystal River Valley at the Penny Hot
Springs and Filoha Meadows. It is very impor-
tant to report any sightings of this weed to the
County Land Manager, so that it can be treated
immediately and not allowed to spread any further.
Biological control:
Insect species have been used in trials, but since Sulfur
cinquefoil is similar to strawberries, the insects used are
considered pests. For more information, contact the Colo-
rado Department of Agriculture's Insectary in Palisade,
Colorado at 970-464-7916. Note that biological control will
not eradicate a weed.
Cultural control:
The only recommendation available for preventing the spread of this species is by eliminating seed
production from established stands, and discontinuing its use as an ornamental.
Mechanical control:
Mowing is not effective, as new shoots will replace the cut stems. Hand -digging or pulling when
soil is moist is effective on small infestations, if the entire root system is removed. Tillage alone
will spread the infestation, since root fragments will produce new plants.
Chemical control:
Contact the Pitkin County Land Management Department for more specific information about herbi-
cide products, application rates, and equipment calibration.
K. Sulfur Cinquefoil (Potentilla recta) (continued)
Look-Alikes:
There are over 20 native species of Cinquefoil (Potentilla) in Colorado. Many can be easily con-
fused with the noxious weed Sulfur Cinquefoil. They all have yellow, 5-petaled flowers, and most
are herbaceous plants with a creeping or upright growth habit. The exception are the Shrubby
Cinquefoils, (e.g. P. fruticosa) which are small, round bushes with yellow flowers, commonly used
in landscaping. There are three major ways to distinguish the native plants from the noxious weed:
• Flower Color: Native Cinquefoils typically have bright yellow blooms, while the flowers
of Sulfur Cinquefoil are usually a paler yellow.
• Stem Hairs: Sulfur cinquefoil has long right-angled hairs that are perpendicular to the leaf-
stalks and the stem. (hence the species name P. recta) While the natives may have hairy
stems, these hairs do not stand straight out.
• Leaf Color: The underside of the leaves of native Cinquefoils are typically silvery -grey
Beautiful Cinquefoil
(Potentilla pulcherrima)
Note bright yellow flowers and prostrate growth habit (left), as well as silvery leaf underside (right).
(Sulfur Cinquefoil is erect with pale yellow flowers and a leaf that is dark green on both sides)
and often hairy, while Sulfur cinquefoil leaves are dark green on both sides.
Shrubby Cinquefoil
(Potentilla fruticosa)
Note its woody, shrub -like growth habit, bright
yellow flowers, and small, narrow leaves.
(Sulfur Cinquefoil is herbaceous and pale yellow
flowers and large, palmately compound leaves.)
L. Dame's Rocket
(Hesperis matronalis)
Key Characteristics:
Dame's Rocket is an escaped ornamen-
tal. It grows as a biennial or short-lived
perennial, ranging in height from 1 to 4
feet tall. Flowers range in color from
white to pink to purple and consist of 4
petals arranged in the cross shape dis-
tinctive of the Mustard family. Leaves
are lanceolate and somewhat wooly in
texture, with finely -toothed margins.
Fruit is a silique.
Locations:
Although rare in Colorado overall, this
escaped ornamental is often found in
and around garden sites throughout the
Roaring Fork Valley. It is particularly
common in Snowmass Village and As-
pen, but can be found in Old Snowmass
and the Pitkin County portion of Basalt,
as well as in the Crystal River Valley.
Dame's Rocket particularly likes ripar-
ian areas and Aspen forest sites, where
it quickly invades and displaces valu-
able native vegetation.
Biological control:
None known at this time.
Cultural control:
Do not plant this weed. There are many equally stunning native alternatives, such as varieties of
Penstemon, Columbine, and Echinacea. Contact Land Management for suggestions.
Mechanical control:
Pulling or cutting is very effective. Be sure to bag and dispose of any seed pods present.
Chemical control:
Contact the Pitkin County Land Management Department for more specific information about herbi-
cide products, application rates, and equipment calibration.
L. Dame's Rocket (Hesperis matronalis) (continued)
Native Look-Alikes:
Fireweed
(Chamerion angustifolium)
Dame's Rocket is commonly confused with native Fireweed
(left), which has a similar shape and flower color.
The purple flowers of Fireweed have long styles that termi-
nate in four stigmas (below). In addition, the petals of Fire-
weed are tapered toward the center and more delicate look-
ing.
Another distinctive feature of
Fireweed is its fruit. The long
seed capsule splits open in late
summer to expose minute
brown seeds with long silky
hairs (right).
Alpine Wallflower
(Erysimum capitatum)
This native wildflower is also a Mustard and
looks very similar to Dame's Rocket, but it is
typically orange, maroon, or yellow.
Note the long seed pods (siliques) present.
These two -chambered fruits are characteristic
of the Mustard family, and are similar to those
made by Dame's Rocket.
M. Poison Hemlock
(Conium maculatum)
Key Characteristics:
Poison hemlock is a member of the Parsley family. It
is a biennial introduced from Europe that may grow
up to 9 feet tall. It has a fleshy, stout taproot and
grows its first year above ground as a fern -like ro-
sette of pinnately divided leaves. Stems of Poison
Hemlock have purple spots at all growth stages. The
white flowers are borne in umbels, each supported by
a stalk.
All plant parts are extremely poisonous to humans
and most domestic livestock. The plants contain the
intensely poisonous alkaloid coniine and other related
alkaloids. Children have been poisoned by using the
hollow stem as a whistle. Adults have been poisoned
by mistaking leaves for parsley, roots for parsnips, or
seeds for anise. The plant has an unpleasant taste and
odor. Symptoms of poisoning are a burning sensation
in the mouth and throat, nervousness, trembling, un-
coordinated body movements, dilation of pupils, mus-
cular weakness, coldness of extremities, weakened and slowed heart-
beat, convulsions, and coma. Death occurs through respiratory pa-
ralysis. Socrates was killed with a formulation of Poison Hemlock.
Locations:
Poison hemlock is very widespread in Pitkin County. It is common on
East and West Sopris Creek, Prince Creek, Watson Divide, and
Woody Creek Roads and in Lenado and Snowmass Village.
Biological control:
The larvae of the Defoliating Hemlock Moth,
Agnopterix alstroemeriana, chew holes in the leaves and flowers of
Poison Hemlock, and feed on seeds prior to pupation. Attacked hem-
lock plants are extensively defoliated and damaged in the first season of
release. Populations of the moth have been released in
Snowmass Village and Woody Creek, and seemed to
cause substantial damage in their first season. However,
it not yet clear whether they have been able to over -
winter and reproduce at our altitude.
Cultural control:
Good vegetative cover lessens likelihood of initial infes-
tations of poison hemlock.
M. Poison Hemlock (Conium maculatum) (continued)
Mechanical control:
Tillage, digging, and pulling are all effective controls
but care must be used when handling. Gloves, eye and
mouth protection are recommended, to guard against
inadvertent contamination by the extremely poisonous
sap of this weed.
Chemical control:
There are some herbicides available that are effective
against Poison Hemlock. However,
because this plant tends to grow near water and wet-
lands, herbicide treatment may not be
appropriate. Contact Pitkin County Land Management
Department for more specific information about herbi-
cide products, application rates, and equipment calibra-
tion.
Native Look-Alikes:
There are many native members of the Parsley family
that look very similar to Poison Hemlock. A couple of
examples are pictured to the right. Do not ingest any
plant unless you are absolutely positive of its identi-
fication.
Cow Parsnip
(Heracleum sphondylium)
Stem thicker, leaves much larger and less
subdivided than Poison Hemlock.
-410
410
Porter's Loveage/Osha
(Ligusticum porteri)
Leaflets somewhat more rounded, and umbels
somewhat less compact than Poison Hemlock.
Porter's Loveage may have purple striations simi-
lar to that on Poison Hemlock. These two plants
are very similar and misidentification is common.
N. Hoary Cress ("Whitetop")
(Cardaria draba)
Key Characteristics:
Hoary cress, a member of the Mustard family, was
probably introduced from Europe in alfalfa seed. It is
a perennial which reproduces by both root and seed.
The extensive root system spreads horizontally and
vertically with frequent shoots arising from the root-
stock. Growth begins in the early spring from a ro-
sette, with bolting, flowering and seed -set occurring
my early to mid -summer. Whitetop grows erect
from 10 to 18 inches high. Flowers are 4-petaled,
white, about 1/8 inch across, and numerous in com-
pact, flat-topped clusters. Leaves have a blue-green
hue. Lower leaves are stalked; upper leaves are al-
ternate, clasp the stem, and are oval or oblong with
toothed or almost smooth margins. Each leaf is 1/2 to
2 inches long with blunt ends.
Locations:
Whitetop is becoming increasingly common in parts
of Pitkin County. It is extremely prolific and moving
quickly throughout the Little Elk Creek and Old
Snowmass areas towards East Sopris Creek. Hoary cress is one of the
emerge in the spring. Flowers are produced in late April and May.
Biological control:
No known biological controls at this time.
earliest perennial weeds to
Cultural control:
Mowing or cultivation effectiveness will be increased if other plants like perennial native grasses or
alfalfa are seeded in the whitetop stands as competitors. Maintain range and pasture in good condi-
tion. Promote healthy grass growth through proper irrigation and fertilization. Do not overgraze.
Mechanical control:
Tilling will increase infestation due to extensive underground root system. Cutting and removal of
top growth is somewhat effective. Repeated cutting/mowing may reduce production and spread of
seed.
Chemical control:
There are some herbicides available that are effective against Hoary Cress. Herbicide treatment is
most effective when applied before bloom or in the fall. Contact Pitkin County Land Management
Department for more specific information about herbicide products, application rates, and equip-
ment calibration.
N. Hoary Cress (Cardaria draba) (continued)
Native Look-Alikes:
Field Pennycress
(Thlaspi arvense)
Field Pennycress is a non-native,
non -noxious weed that often ap-
pears as a pioneer species in areas
of recent ground disturbance.
While non-native, Pennycress is
not very aggressive and thus not a
very pernicious threat to native
vegetation. However, it is often
confused with Hoary Cress, which
looks similar at early growth
stages.
The foliage
of Field
Pennycress
is generally
more coarsely toothed than
Hoary Cress and lacks the
latter's blueish -green hue.
The fruit is a distinctive
"penny" shaped silicle.
Yarrow
(Acillea lanulosa)
Distinguish Yarrow from Hoary Cress by its
O. Houndstongue ("Beggar's Lice")
(Cynoglossum officinale L)
Key Characteristics:
Houndstongue is a member of the Borage family. A bien-
nial introduced from Europe, it reproduces only by seed
and lives its first year as a leafy rosette. The stout, erect,
stem appears the second year, growing 1-4 feet high.
Leaves are alternate, oblong to lance -shaped, 1-12 inches
long, 1-3 inches wide, lacking teeth or lobes, and with
soft, white hairs. Leaves often appear dusty or insect -
ridden, and may have reddish streaks. Flowers are red-
dish -purple in color. The fruit consists of four nutlets,
each about 1/3 inch long. The seeds are covered in short
prickles which act like Velcro and are rapidly scattered
by animals, socks, shoes, etc. Houndstongue is toxic to
horses, livestock, and wildlife, containing pyrrolizidine
alkaloids that can stop liver cells from reproducing. Ani-
mals may live up to six months after ingesting a lethal
dose.
Locations:
A prolific seed producer and excellent hitch -hiker, Houndstongue is widespread
throughout Pitkin County, particularly in areas of past or current livestock grazing, but
also along hiking trails, in riparian zones, and other high -traffic areas.
Biological control:
No known biological controls at this time.
Cultural control:
Re -seed disturbed sites with fast-growing native grasses.
Maintain range and pasture in good condition. Promote
healthy grass growth through proper irrigation and fertiliza-
tion. Particular care should be taken not to overgraze pas-
tures where Houndstongue is present, as likely hood of lethal
ingestion by livestock is greatly increased. Caution should
also be taken not to purchase or distribute contaminated hay,
as dried and diluted Houndstongue leaves are more palatable
to animals.
Mechanical control:
The key to managing Houndstongue is to keep seeds from
spreading. This is best achieved by pulling or digging the
plant at flowering or early seed formation, bagging, and removing plants. Regular cultivation, dig-
ging, pulling and cutting are effective if done frequently — the plant's hearty taproot can support
several re -sprouts in one season if not removed.
Chemical control:
Contact Pitkin County Land Management Department for more specific information about herbicide
products, application rates, and equipment calibration.
P. Diffuse Knapweed
(Centaurea diffusa)
Key Characteristics:
Diffuse knapweed is a member of the Sunflower
family. Diffuse knapweed was introduced from
Europe and is a biennial or short-lived perennial that
reproduces by seed only. The plant usually produces
a single main multi -branched stem that is 1 1/2 to 2
feet tall. The flower is white or pink with spiny
bracts with a pronounced tip and fringed edges.
Leaves are finely divided, existing as a ground -level
rosette in the first year of growth. Seedheads are
retained, and plant becomes a tumbleweed in winter,
spreading seed along its way.
Locations:
The largest infestations are found at the base of
Smuggler Mountain Road and in Snowmass Village
across from the Snowmass Conoco. Plants have also
been found along Medicine Bow Road. An early de-
tection and early treatment philosophy could eradicate
this weed in Pitkin County.
Biological control:
There are several insects available for release and control of large
infestations of knapweed. These include two Seed -Head Gall Flies
(Urophora affinis and U. quadrifasciata), the Sulfur Knapweed
Root Moth (Agapeta zoegana), the Knapweed Flowerhead Weevil,
Larinus minutus, and the Knapweed Seed Head Moth (Metzneria
paucipunctella). Note that biological control is useful to reduce the
size of large infestations, but will not result in eradication of the
weed.
Cultural control:
Competitive vegetation helps resist infestation, but can still be displaced. Proper fertilization and
irrigation will generally support competitive native grass stands. Do not overgraze.
Mechanical control:
The key to managing Diffuse Knapweed is to prevent it from going to seed. This is best achieved by
pulling or digging the plant at rosette, flowering or early seed formation stages, then bagging, and
removing plants. Regular cultivation, digging, pulling and cutting are effective if done frequently;
the plant's hearty taproot can support several re -sprouts in one season if not removed.
Chemical control:
Contact Pitkin County Land Management Department for more specific information about herbicide
products, application rates, and equipment calibration.
Q. Meadow Knapweed
(Centaurea pratensis)
Key Characteristics:
Meadow knapweed is a member of the Sunflower
family. It is a perennial that grows 2-4 feet tall, con-
taining many branches each terminating in a single
flower. Leaves are not finely divided like they are
with spotted and diffuse knapweed. Lower leaves
are entire, coarsely lobed, or toothed, while middle
and upper leaves are entire or toothed. Flowers
are large pink to purplish -red heads at the end of the
branches; Bracts are papery, fringed, and k brown.
Locations:
Meadow knapweed is rare in Pitkin County, but has
been identified in the Little Elk Creek subdivision.
This infestation has been monitored and treated
since 2006, and is believed to be nearly eradicated.
Biological control:
There are several approved biological control agents
for meadow knapweed. For most effective control, use a combination of
several different kinds of insects. Contact the Colorado Department of
Agriculture Insectary in Palisade for more information.
Cultural control:
Meadow knapweed tends to form monocultures by eliminating other
plants. Therefore, sowing desirable plant species is necessary after the
weed is controlled. If a meadow knapweed stand is not too old and
grasses are still present, stimulating grass growth by irrigation (where
possible) should increase grass competition with knapweed and keep it
under continual stress. It will still be necessary to remove flowers be-
fore they set seed to prevent infestation of new areas.
Mechanical control:
Plants that are periodically mowed will generally continue to flower and produce seed on shorter
plants below the mower blade. Repeated cultivation can be effective if combined with monitoring
for and control of re -sprouts.
Chemical control:
Contact Pitkin County Land Management Department for more specific information about herbicide
products, application rates, and equipment calibration.
R. Russian Knapweed
(Acroptilon repens)
Key Characteristics:
Russian knapweed is a member of the
Sunflower family introduced from
Europe. It is a perennial that reproduces
by seed and creeping, horizontal roots.
Upright, branched, stiff, stems grow 1
to 3 feet high. Flowers develop June -
August and are 1/4-1/2 inches wide,
pink to lavender, with distinctive papery
bracts. Russian Knapweed is allelo-
pathic, meaning it contains a toxic sub-
stance that inhibits the growth of com-
peting plants. This trait, combined with
the plant's extensive root system and
prolific seed production, make Russian Knapweed very difficult to control once
established.
This plant can be toxic to horses, when consumed over time. Once poisoning occurs horses are
unable to chew or advance food to the back of their mouths; swallowing and drinking are severly
impaired. Poisoning is irreversible and death by starvation will occur.
Locations:
Numerous small patches of Russian Knapweed exist along Hwy 133 and Snowmass Creek Road
from Windstar to the end of the asphalt. It is also found along Brush Creek Road and in the Town of
Snowmass Village, as well as on Aspen Valley Ranch in Old Snowmass and Stark Mesa above the
Crystal River. The key to Russian knapweed control is to stress the weed until it expends nutrient
stores. An Integrated Management Plan should be developed that combines revegetation with me-
chanical and/or chemical control. A single strategy used alone is typically inadequate.
Biological control:
A gall -forming nematode established in Washington may eventually be available. Contact the Colo-
rado Department of Agriculture Insectary in Palisade for more information.
Cultural control:
Russian knapweed tends to form monocultures by eliminating other plants through allelopathy and
aggressive nutrient consumption. Thus, it is important to combine weed control with revegetation.
If a Russian knapweed stand is not too old and grasses are still present, stimulating grass growth by
irrigation (where possible) should increase grass competition with knapweed and keep it under con-
tinual stress.
Mechanical control:
Mowing, pulling and cultivation are ineffective control methods because they do not address the
plant's creeping root system (and, in the case of tillage, may actually spread the infestation).
Chemical control:
Timing is critical: apply herbicides at bud stage or after a light frost. Contact Pitkin County Land
Management Department for more specific information about herbicide products, application rates,
and equipment calibration.
S. Spotted Knapweed
(Centaurea maculosa)
Key Characteristics:
Spotted knapweed is a member of the Sunflower family. Native
to central Europe, it is a simple perennial that reproduces from
seed and forms a new shoot each year from a taproot. The plant
can have one or more shoots up to 4 feet tall. Flowers are usu-
ally lavender to purple with spotted bracts. Spotted knapweed
tolerates dry conditions, similar to diffuse knapweed, but will
survive in higher moisture areas as well.
Locations:
Spotted knapweed is one of the most invasive, aggressive weeds
to plague the western United States. Very rare in Pitkin County,
the largest infestation is found in patches along State Highway 82
from east of Aspen to Tagert Lakes. This infestation has been
monitored and treated yearly. It is imperative that this infestation
not be allowed to spread into the fragile sub -alpine ecosystem.
Biological control:
There are several insects available for release and control of large infestations of knapweed. These
include two Seed -Head Gall Flies (Urophora affinis and U. quadrifasciata), the Sulfur Knapweed
Root Moth (Agapeta zoegana), the Knapweed Flowerhead Weevil, Larinus minutus, and the Knap-
weed Seed Head Moth (Metzneria paucipunctella). Note that biological control is useful to reduce
the size of large infestations, but will not result in eradication of the weed.
Cultural control:
If desirable grass competition is evident in spotted knapweed stands, judicious herbicide applica-
tion that does not injure grasses may release the grass to compete effectively with the weeds. Irri-
gation may help stimulate grass competition in these cases. Seeding suitable perennial grasses is
necessary to prevent weed re -invasion.
Mechanical control:
Tillage, digging, pulling and cutting will reduce or eliminate plants if repeated frequently, thor-
oughly and prior to seed production.
Chemical control:
Timing is critical: apply herbicides at rosette or early bolt
stage. Contact Pitkin County Land Management Depart-
ment for more specific information about herbicide prod-
ucts, application rates, and equipment calibration.
Native Look-Alikes:
Our native Tansyaster (Machaeranthera bigelovii),
can resemble Spotted or Russian Knapweed before
flowers fully open. This daisy -like bloom has purple
ray flowers surrounding a yellow center and sticky,
back -curving bracts beneath.
T. Common Mullein
(Verbascum thapsus)
Key Characteristics:
Common mullein is a member of the Snapdragon family. It was
introduced from Europe, but is native to Asia. A deep tap -rooted
biennial growing up to 7 feet tall, it produces a large rosette up
to 2 feet in diameter the first year. Leaves are large, soft, and
very hairy leaves. It produces a large rosette up to 2 feet in di-
ameter the first year. Flowers are yellow and borne in large ter-
minal spikes. Dipped in tallow, mature stalks made good torches
in ancient times; called "witch's -stick".
Locations:
Found throughout Pitkin County along dried-up river bottoms,
pastures, meadows, fencerows and disturbed areas. Especially
prevalent on gravelly soils.
Biological control:
None present and no current research.
Cultural control:
Good vegetative cover is the best way to avoid proliferation of Common Mullein.
Mechanical control:
Will not stand tillage. Pulling or cutting below the root crown when soil is damp is effective if done
prior to seed production.
Chemical control:
Only effective when combined with adequate surfactant to allow penetration of hairy leaves. Contact
Pitkin County Land Management Depai lenient for more specific information about herbicide prod-
ucts, application rates, and equipment calibration.
U. Oxeye Daisy
(Chrysanthemum leucanthemum)
Key Characteristics:
Oxeye daisy, a member of the
Sunflower family, is native to
Eurasia and was introduced to
the West as an ornamental.
Having escaped cultivation, this
pretty little plant now crowds
out important native vegetation
in sensitive riparian ecosystems
and has become an aggressive
and difficult noxious weed. Ox-
eye Daisy grows as an erect,
rhizomatous perennial. Showy
blossoms are a composite of
white ray (outer) and yellow
disk (inner) flowers, blossoming
from June to August. Lower
leaves are spoon -shaped and appear somewhat waxy;
upper leaves are narrow and clasp the stem.
Locations:
Originally planted intentionally in Pitkin County in wildflower mixes, this escaped ornamental has
spread throughout Pitkin County. Especially common in and around the Redstone area, it is begin-
ning to dominate the Crystal River drainage area. It is also very common in the City of Aspen and
Town of Snowmass Village, and can be found throughout Old Snowmass and Woody Creek as
well. Alternatives to planting oxeye daisy include native daisies, black-eyed susan, Shasta daisy,
and blanket flower.
Biological control:
No known biological controls at this time.
Cultural control:
The key to oxeye daisy management is to
create strong awareness among homeowners,
nurseries, landscapers, and landscape archi-
tects that this is a noxious weed and therefore
should not be specified in plantings, sold in
nurseries, or planted in home gardens or
large-scale landscape projects.
Mechanical control:
Repeated tillage or digging will eventually
eliminate rhizomes.
Chemical control:
Contact Pitkin County Land Management Department for more specific information about herbicide
products, application rates, and equipment calibration.
U. Oxeye Daisy (Chrysanthemum leucanthemum) (continued)
Look-Alikes:
Oxeye Daisy is often confused with the non-native ornamental Shasta daisy (Leucanthemum x su-
perbum). This confusion is often complicated by the fact that wildflower seed mixes labeled as con-
taining Shasta daisy are often contaminated with Oxeye. Shasta is generally more robust than Ox-
eye and has larger flowers and foliage, as illustrated by the side -by -side comparison below. Both
are prolific seed producers, but in contrast to Shasta daisy (which grows from a root ball) Oxeye has
a creeping root system that further allows it to escape cultivation and become quickly and substan-
tially established neighboring wildlands.
Oxeye Daisy (noxious)
Shasta Daisy (cultivated)
Shasta (above) versus Oxeye (right)
The leaves of the noxious weed are smaller
and more deeply lobed than the broad, long
leaves of the cultivar.
V. Perennial Pepperweed
("Tall Whitetop")
(Lepidium latifolium)
Key Characteristics:
Perennial Pepperweed is a member of the Mustard
family and very similar to Hoary Cress in appearance
and management. It is a deep-rooted perennial plant
with an extensive, vigorous, creeping root system.
Perennial Pepperweed stands 1-3 feet high (up to 5 feet
in wet areas) with a heavy, sometimes woody, crown.
Leaves are waxy with a distinctive white midrib.
Lower leaves are oblong with toothed margins; upper
leaves are lack a petiole but do not clasp the stem.
Flowers are very white and found in dense rounded
clusters.
Perennial Pepperweed can be found in pastures, ripar-
ian areas, roadsides, and waste places. This weed has
taken over thousands of acres in the San Luis Valley.
Locations:
This plant is found along Hwy 82 in Snowmass Can-
yon, with a few patches between Old Snowmass and
Basalt. It is very difficult to control and should not be
allowed to spread.
Biological control:
No known biological controls at this time.
Cultural control:
Re -seed disturbed sites with fast-growing native
grasses. Maintain range and pasture in good condition.
Promote healthy grass growth via proper irrigation and
fertilization.
Mechanical control:
Repeated hand pulling and digging are good for limited
infestations. Clean tillage equipment to avoid spreading
roots. Do not overgraze.
Chemical control:
Contact Pitkin County Land Management Department
for more specific information about herbicide products, application rates, and equipment calibration.
V. Perennial Pepperweed (Lepidium latifolium) (continued)
Native Look-Alikes:
Field Pennycress
(Thlaspi arvense)
Field Pennycress is a non-native,
non -noxious weed that often ap-
pears as a pioneer species in areas
of recent ground disturbance.
While non-native, Pennycress is
not very aggressive and thus not a
very pernicious threat to native
vegetation. However, it is often
confused with Hoary Cress, which
looks similar at early growth
stages.
The foliage
of Field
Pennycress
is generally
more coarsely toothed than
Hoary Cress and lacks the
latter's blueish -green hue.
The fruit is a distinctive
"penny" shaped silicle.
Photo bw Robert Nape!
Yarrow
(Acillea lanulosa)
Distinguish Yarrow from Hoary Cress by its
wooly, finely -divided leaves and hairy stems.
W. Russian Olive
(Elaeagnus angustifolia)
Key Characteristics:
Russian olive is a member of the Oleaster family. A hardy, fast-
growing tree introduced from Europe, Russian olive has been pro-
moted for windrow and ornamental plantings. Russian olive can be
found in both dry and moist soils, but does particularly well in
sandy flood plains. This tree may reach heights of 10 to 25 feet.
The trunk and branches are armed with 1 to 2 inch woody thorns.
Leaves are covered with small scales which give the foliage a dis-
tinctive silvery appearance. Flowers are yellowish -green in color
and produce a berry -like fruit that silvery when first formed but
turns brown at maturity. Russian Olive is rapidly replacing native
riparian species and eliminating valuable nesting sites for birds. It
should be eliminated whenever possible.
Locations:
To date Russian olive has not been a problem in Pitkin County but
has the capability to spread if left unchecked. This weed is starting
to establish itself along the Crystal River, Roaring Fork, and Snow -
mass Creek valleys. Mapping and monitoring efforts have begun in
2009 and will help determine whether infestations are spreading.
Biological control:
No known biological controls at this time.
Cultural control:
Do not plant or propagate Russian Olive. Landscape with native
trees wherever possible. Plant and support native vegetation in ri-
parian areas.
Mechanical control:
Russian Olive saplings and sprouts can be hand -pulled or removed
with a shovel or other appropriate hand -tool. Do this when the soil
is moist to insure removal of the root system. For larger trees, cut-
ting alone (i.e. without herbicide treatment) will actually promote
denser re -growth. Burning during the dormant season also results
in vigorous re -sprouting.
Chemical control:
Contact Pitkin County Land Management Depai liiient for more
specific information about herbicide products, application rates,
and equipment calibration.
X. Salt Cedar (Tamarisk)
(Tamarix chinensis; T. ramosissima)
Key Characteristics:
Salt cedar, also known as Tamarisk, was introduced
from Eurasia and is now wide -spread in the United
States. Salt cedar is a member of the Tamarisk family.
It is a deciduous or evergreen shrub or small tree that
grows from 5 to 20 feet tall. The bark on saplings and
stems is reddish brown. Leaves are small and scale -
like and flowers are pink to white and five -petalled.
The stems and leaves of mature plants secrete a salt
that forms a crust above and below ground and inhibits
native plants from establishing.
Locations:
In Pitkin County, Salt Cedar has most recently been
found along the river and retaining ponds at Wingo
Ranch, and along Hwy 82 in Snowmass Canyon. Infesta-
tions in the Crystal River by Penny Hot Springs are be-
lieved to have been eradicated. Salt Cedar is very preva-
lent along the Colorado River. It is extremely important
that anglers and boaters clean their waders, equipment, and
boats before leaving infested areas so as not to bring this
invader into the upper Roaring Fork Valley.
Biological control:
The Salt Cedar Leaf Beatle (Diorhabda elongata) eats the
leaves of Salt Cedar causing stem dieback and potential death of the plant if defoliation is consistent.
Populations have been released in eastern Utah and have crossed the border into Western Colorado.
The beetle is available for limited distribution. Contact the Colorado Department of Agriculture
Insectary in Palisade for more information.
Cultural control:
Competitive vegetative cover helps but cannot prevent spread in susceptible sites. After a Salt Ce-
dar infestation is managed, revegetation is necessary to protect the soil resource and reduce the
threat of reinvasion. Seeded grasses, willow stakes, and cottonwood cuttings can reduce the chance
of Salt Cedar re-entering managed sites.
Mechanical control:
For small infestations, cut -stump treatments are effective. This means felling via chainsaw or lop -
per, followed by an application of herbicide directly to the cambium. A bulldozer or prescribed fire
can be used to open up large stands of salt cedar for access for further control. To be effective, these
methods should be followed up with an herbicide treatment of the re -sprouts when they are 1-2 me-
ters tall.
Chemical control:
Contact Pitkin County Land Management Department for more specific information about herbicide
products, application rates, and equipment calibration.
Y. Cypress Spurge
(Euphorbia cyparissias)
Key Characteristics:
Cypress Spurge is a member of the Spurge
family. It is a perennial that reproduces by
both seed and an extensive creeping root
system. Leaves are alternate, numerous,
small, and narrow. Stems are very branched
toward their upper ends and reach 4-32
inches in height. When severed, stems se-
crete a milky latex that is toxic to horses
and cattle and caustic to human skin. Heart -
shaped, leaf -like bracts form below incon-
spicuous flowers. These bracts are yellow-
ish -green early in the season, turning reddish -green toward matur-
ity. Flowers are yellowish -green and form at the tips of the main
stem and upper branches.
Locations:
Cypress Spurge is known to exist in two small patches on private
land in Old Snowmass. It appears to have been planted as an orna-
mental.
Biological control:
None available at this time. Note that the Colorado Department of
Agriculture does not accept Biological Control as an acceptable
method for List A noxious weed species.
Cultural control:
Do not plant Cypress Spurge! Maintain healthy native
vegetation to prevent infestation. Survey your land
regularly to detect new invaders. Quickly eradicate any
new populations.
Mechanical control:
Hand -pulling or digging can be effective when manag-
ing new, small infestations and care is taken to remove
the entire root system. Tillage may encourage spread by
further dispersing rhizomes. When handling plants wear
rubber gloves and eye protection to protect yourself
from the irritating milky sap.
Chemical control:
Contact Pitkin County Land Management Department
for more specific information about herbicide products, application rates, and equipment calibration.
Z. Leafy Spurge
(Euphorbia esula)
Key Characteristics:
Leafy spurge is in the Spurge family. It is a perennial
that reproduces by seed and an extensive creeping root
system that makes it difficult to control once established.
Roots can extend as deep as 30 feet! The plant grows 1-
3 feet tall with pale green shoots and inconspicuous yel-
low -green flowers enclosed by a pair of yellow -green,
heart -shaped bracts that have the appearance of flower
petals. The plant, including the root, contains a milky
latex that is damaging to eyes and caustic to skin.
Locations:
Leafy Spurge infestations occur in the Woody Creek Val-
ley and along the Roaring Fork basin from Twining Flats
to the Star Mesa subdivision. The Leafy Spurge flea
beetle has been released nearly annual in these areas for
over a decade and seems to have made some difference
in reducing infestation density. Patches of Leafy Spurge
also exist on the West Buttermilk subdivision.
Biological control:
Sheep or goats will graze leafy spurge. If livestock graze leafy spurge after seed formation, hold
animals in a corral for at least seven days before moving them to an un-infested area to avoid
spread of any seeds or root -parts.
There are also several insects available for Leafy Spurge control. Each feeds on a specific part of
the plant. When used together, these insects can provide very effective reduction in large, con-
tiguous infestations. Insects available include:
• species of the flea beetle, Apthona, whose larvae feed on primary and secondary roots. A va-
riety of several complementary Apthona species are typically sold together for release.
• the Red -Headed Spurge Stem Borer (Oberea erythrocephala) — a long -horned beetle that
feeds on leaves, bracts, and girdles of stems and is able to survive in shady release sites,
unlike the flea beetle species above.
• the Spurge Shoot -Tip Gall Midge (Spurgia esulae), which lays its eggs upon the shoot tips
of the plant and produces two or three generations per year. Feeding larvae stress the plant
and help preventing flowering and seed production on the attacked stem.
Cultural control:
Any activity which encourages vigorous grass growth is very important. Do not overgraze.
Mechanical control:
Persistent, almost zealous digging or cultivation is required to be at all successful. Mowing leafy
spurge at 14-21 day intervals may cause higher susceptibility to fall applied herbicides.
Chemical control:
Contact Pitkin County Land Management Department for more specific information about herbicide
products, application rates, and equipment calibration.
AA. Myrtle Spurge
("Donkey Tail Spurge")
(Euphorbia myrsinites)
Key Characteristics:
Myrtle spurge is a highly invasive
ornamental plant, popular for use in
xeriscapes and rock gardens. This
plant is rapidly expanding into sen-
sitive ecosystems, displacing native
vegetation, reducing forage, and, in
some cases, injuring wildlife. Myr-
tle spurge is a low -growing, tap -
rooted perennial with trailing
stems of fleshy, blue-green, leaves.
This growth form has given rise to
the alternate name, "Donkey -Tail
Spurge." Inconspicuous flowers are surrounded by yellow -green petal -like bracts that first appear
in early spring. Myrtle spurge reproduces by seed and plant fragments, and is capable of projecting
seeds up to 15 feet. This plant exudes toxic, milky latex which can cause severe irritation to skin and
mucus membranes.
Locations:
This plant has been known to occupy ornamental gardens on Red Mountain and in Brush Creek Vil-
lage, the Crystal River Valley, Emma, the City of Aspen, and the Town of Snowmass Village.
Large infestations of Myrtle Spurge exist in the City of Glenwood Springs.
Biological control:
No known biological controls at this time.
Cultural control:
Do not plant Myrtle Spurge. If present, do not allow to seed. Re -vegetate disturbed Areas.
Mechanical control:
For small patches of Myrtle Spurge, diligent pulling/digging can be effective. It is important to get
the entire root and not leave any plant fragments behind. Make sure to wear protective clothing to
protect your skin and eyes against the irritating latex.
Chemical control:
Contact Pitkin County Land Management Depailtnent for more specific information about herbicide
products, application rates, and equipment calibration.
Native Alternatives:
There are several native alternatives to Myrtle Spurge for your xeriscaping or rock garden. These
include Sulfur Flower (Erigonum umbellatum), Kinnikinnick (Artcostaphylos uva-ursi), Oregon
Grape (Mahonia repens), and Yellow Stonecrop (Amerosedum lanceolatum).
BB. Common Tansy ("Garden Tansy")
(Tanacetum vulgare)
Key Characteristics:
Common Tansy is a member of the Sunflower fam-
ily. Originally imported from Europe as an ornamen-
tal, it is a perennial plant that grows from 1'/2 to 6
feet tall with yellow button -like composite flowers
and fern -like leaves. Reproducing by both seed and
an extensive root system, tansy is difficult to con-
trol. Tansy is particularly aggressive when growing
along irrigation ditches where it can restrict water
flow.
Locations:
Common Tansy is found throughout Pitkin County,
usually in small dense patches in sub -irrigated areas
along roads, ditches, and in waste areas and pastures.
Just down -valley of the county line, Common Tansy dominates the Hwy 82 and Rio Grande Trail
rights -of -way, making up -valley transport of seed inevitable. This extremely aggressive weed is
also often found as an ornamental in gardens throughout the valley. See below for native alterna-
tives.
Biological control:
No known biological controls at this time.
Cultural control:
Do not plant Common Tansy. Competitive vegetative cover helps but does not completely prevent
infestation.
Mechanical control:
Repeated mowing or cutting will inhibit seed production, and may stress root system. Pulling and
digging are usually ineffective, as these can actually stimulate roots to spread.
Chemical control:
Contact Pitkin County Land Management Department for more spe-
cific information about herbicide products, application rates, and
equipment calibration.
Look-Alikes:
Common Tansy can easily be confused Yellow Yarrow, a common
garden plant that looks very similar to the noxious weed, but can be
distinguished by its grayish -green, wooly leaves, and flower clusters
that are more umbrella -like than button -shaped.
Yellow Yarrow
CC. Bull Thistle
(Cirsium vulgare)
Key Characteristics:
Bull thistle is a member of the Sunflower family. It is a
biennial, living its first year as a low -growing rosette,
up to 1 foot in diameter; Bull Thistle bolts in its second
year to produce a stem 2 to 5 feet tall, bearing many
spreading, slightly hairy branches with spiny wings.
Leaves are alternate, 3-12 inches long, pinnately-lobed,
hairy and prickly on the upper side while cottony under-
neath. Gumdrop -shaped blooms appear July through
September and are pink to dark purple and 11/2 to 2
inches in diameter. Involucres are somewhat tapered
and covered with spines. Seeds are capped with a circle
of plume -like white hairs.
Locations:
Bull thistle can be found in the Crystal River Valley and
Capitol Creek regions. Plants have also been found in
Snowmass Village and at the Pitkin County Airport.
Biological control:
The Thistle Stem Gall Fly, Urophora stylata, is used to help control this thistle. Females lay eggs
on the seed -head. The maggot then consumes the seed in the flower. This species has over -
wintered in Colorado, but the limited numbers will not allow for general redistribution. For more
information contact the Colorado Department of Agriculture Insectary in Palisade.
Cultural control:
Good vegetative cover helps slow establishment, but Bull Thistle can invade healthy stands includ-
ing healthy lawns.
Mechanical control:
Bull thistle will not withstand regular cutting or tillage. Don't let it go to seed; carefully cut and bag
if flower heads are present.
Chemical control:
Contact Pitkin County Land Management Department for more specific information about herbicide
products, application rates, and equipment calibration.
Native Look-Alikes:
There are several Native Thistles in Pitkin County which may be confused with Bull Thistle. See
Appendix B for more information about Native Thistles.
DD. Canada Thistle
(Cirsium arvense)
Key Characteristics:
Canada thistle is a member of the Sunflower
family. It is a perennial which reproduces by
seeds and fleshy, horizontal roots. The erect
stem is hollow, mostly smooth, and reaches 1 to
5 feet tall, branching at the top. The lower stem
is covered with fine hairs. Flowers are typically
pale pink to lavender, sometimes purple.
Locations:
Canada thistle emerges in June in most parts of
Pitkin County. It is one of the most widespread
and economically damaging noxious weeds in
Colorado. Infestations are found in cultivated fields, riparian areas, pastures, rangeland, forests,
lawns and gardens, roadsides, and in waste areas. Because of its prolific seed production, vigor-
ous growth, and extensive underground root system, control is difficult. Canada thistle is best
managed through an integrated management system that emphasizes competitive desirable
plants.
Biological control:
Cattle, goats, and sheep will graze Canada thistle when plants are tender in the Spring.
There are also currently several insects available for Canada Thistle control:
• Canada Thistle Stem Mining Weevil (Ceutorhvnchus litura) attacks the stem of young Canada
Thistle plants as they emerge from the soil and begin to elongate.
• Canada Thistle Flower Weevil (Larinus planus) feeds on flower heads.
• Defoliating Beetle (Cassida rubiginosa) eats the leaves of Canada, Musk, Plumeless Thistles.
Cultural control:
Maintain soil disturbances, and encourage desirable plant growth.
Mechanical control:
Canada thistle is very difficult to mechanically control because each time a root is cut, it serves to
increase the number of plants; regular cutting or tillage can wear down plant reserves and reduce
population and vigor but results are often erratic.
Chemical control:
Appropriate timing is critical for effective chemical control of Canada Thistle. Application at bud
stage or in the fall after a light frost allow for best translocation of herbicide to the plants' extensive
root system. Contact Pitkin County Land Management Department for more specific information
about herbicide products, application rates, and equipment calibration.
Native Look-Alikes:
There are several Native Thistles in Pitkin County which may be confused with Canada Thistle. See
Appendix B for more information about Native Thistles.
EE. Musk Thistle ("Nodding Thistle")
(Carduus nutans)
Key Characteristics:
Musk thistle is a member of the Sunflower family. In-
troduced from Eurasia, it is a winter annual or biennial
which reproduces by seed. The first year's growth is a
large, compact rosette from a large, corky taproot. The
second year stem is erect, spiny, 2 to 6 feet tall. The
waxy leaves are dark green with a light green midrib
and mostly white margins. Purple or magenta compos-
ite flowers sit solitary on stems, nodding when mature,
with pinecone-like prickly bracts below.
Locations:
This species of thistle was once very widespread in Pitkin County but has been drastically reduced
by the Seed Head Weevil, Rinocillus Conicus. The plant still occurs on Hwy-133 and in a few areas
in Old Snowmass.
Biological control:
When possible, it is best release more than one type of insect on a weed since each type may work
on a different part of the plant. Insects currently available for Musk Thistle control include:
• Musk Thistle Seed Head Weevil, Rhinocyllus conicus, is widespread in Colorado. Larvae of
this insect destroy developing seeds but are not 100 percent effective by themselves. The weevil
normally impacts seed production by about 50 percent. Herbicides can be combined with wee-
vils if the insects are allowed to complete their life cycles. Unfortunately, R. conicus will also
attack native thistle populations.
• Thistle Rosette Weevil, Trichosirocalus horridus, attacks the crown area of musk thistle ro-
settes and weakens the plant before it bolts. This weevil has reduced stand density in areas
where it has become well established.
• Defoliating Beetle (Cassida rubiginosa) eats the leaves of Canada, Musk, Plumeless Thistles.
Cultural control:
Mitigate soil disturbance and encourage desirable plant growth.
Mechanical control:
Mowing, cutting, digging, pulling or cultivation are all effective if done prior to flowering.
Chemical control:
The best timing for chemical control is when plants are in the rosette or early bud stages. Effective
control may require applications in both the spring and fall. Contact Pitkin County Land Manage-
ment Department for more specific information about herbicide products, application rates, and
equipment calibration.
Native Look-Alikes:
There are several Native Thistles in Pitkin County which may be confused with Musk Thistle. See
Appendix B for more information about Native Thistles.
FF. Plumeless Thistle
(Carduus acanthoides)
Key Characteristics:
Plumeless Thistle is a member of the Sunflower family.
Introduced from Eurasia, it is a winter annual or biennial.
This plant can be distinguished from Canada Thistle by the
presence of many spines along its stem and from Musk
Thistle by its smaller blossoms and lack of the prominent
white margin present on musk thistle leaves. The plant
may grow to a height of 5 feet or more and is an extremely
prolific seed producer.. Flowers are magenta to purple and
are either solitary or clustered. Taproot is large and
fleshy.
Locations:
While Plumeless Thistle is common throughout Pitkin
County, it is rare Colorado at large, found primarily in the tri-county area of Eagle, Garfield and
Pitkin Counties.
Biological control:
When possible, it is recommended to release more than one type of insect on a weed since each type
may work on a different part of the plant. Insects available for Plumeless Thistle control include:
• Musk Thistle Seed Head Weevil, Rhinocyllus conicus, is widespread in Colorado. Larvae of
this insect destroy developing seeds but are not 100 percent effective by themselves. The weevil
normally impacts seed production by about 50 percent. Herbicides can be combined with wee-
vils if the insects are allowed to complete their life cycles. Unfortunately, R. conicus will also
attack native thistle populations.
• Defoliating Beetle (Cassida rubiginosa) eats the leaves of Canada, Musk, Plumeless Thistles.
• Thistle Rosette Weevil, Trichosirocalus horridus, attacks the crown area of musk thistle ro-
settes and weakens the plant before it bolts. This weevil has been introduced to Pitkin County,
but appears to be ineffective on Plumeless Thistle.
Cultural control:
Good vegetative cover tends to inhibit establishment but plumeless thistle can invade healthy sites.
The best management is to minimize disturbance and revegetate with competitive perennial species.
Mechanical control:
Mowing, cutting, digging, pulling or cultivation are all effective if done prior to flowering.
Chemical control:
The best timing for chemical control is when plants are in the rosette or early bud stages. Effective
control may require applications in both the spring and fall. Contact Pitkin County Land Manage-
ment Department for more specific information about herbicide products, application rates, and
equipment calibration.
Native Look-Alikes:
There are several Native Thistles in Pitkin County which may be confused with Plumeless Thistle.
See Appendix B for more information about Native Thistles.
GG. Scotch Thistle
(Onopordum acanthium; O. tauricum
Key Characteristics:
Scotch thistle is a member of the Sunflower family.
A biennial, it leaves as a rosette in its first year and
can have leaves up to 2 feet long and 1 foot wide.
Leaves are blueish- or grayish -green, toothed, and
spiny. The second year the plant can grow up to 8
feet tall, with a stalk that has broad spiny wings.
The entire plant is finely hair to wooly. There are 2-
3 large, globe -shaped magenta Flowers per branch
tip, with spiny, needle -like bracts below.
Locations:
Scotch thistle is abundant in Garfield and Eagle
Counties, but relatively rare in Pitkin County. Plants
have been found in the Town of Snowmass Village
and along Emma, Lower River, and Capitol Creek
Roads.
Cultural control:
Competitive vegetation helps limit spaces open to invasion.
Biological control:
The Thistle Stem Gall Fly, Urophora stylata, is used to help control this
thistle. Females lay eggs on the seed -head. The maggot then consumes the
seed in the flower. This species has over -wintered in Colorado, but the lim-
ited numbers will not allow for general redistribution. For more information
contact the Colorado Depai trnent of Agriculture Insectary in Palisade.
Mechanical control:
Mowing can stop seed production in short term, but plants can re -grow; digging, cutting and cultiva-
tion are effective; monitor for new growth all season long; seed bank will be present for 2-4 years.
Chemical control:
The best timing for chemical control is when plants are in the rosette or early bud stages. Effective
control may require applications in both the spring and fall. Contact Pitkin County Land Manage-
ment Department for more specific information about herbicide products, application rates, and
equipment calibration.
Native Look-Alikes:
There are several Native Thistles in Pitkin County which may be confused with Canada Thistle. See
Appendix B for more information about Native Thistles.
HH. Dalmatian Toadflax
"Wild Snapdragon"
(Linaria genistifolia)
Key Characteristics:
Dalmatian toadflax is a member of the Snapdragon
family. It was introduced from Europe as an orna-
mental, but has escaped cultivation and is rapidly
invading Western range- and wild -lands. The
flower of this creeping perennial closely resembles
that of Yellow Toadflax, but the plant can be easily
distinguished by its leaves, which are blue-green,
heart -shaped and clasping the stem. Flowers are
bright yellow with orange centers, snapdragon -like
and spurred. Dalmatian toadflax is especially well -
adapted to arid sites and can spread rapidly once
established. Its deep, extensive root system, waxy
leaves, and heavy seed production, make it diffi-
cult to control.
Locations:
Dalmatian toadflax is still relatively rare in Pitkin County but common in Glenwood Springs.
Singular plants have been found in isolated locations throughout Pitkin County. More substantial
infestations exist along Capitol Creek Road near the Monastery and along Upper Snowmass Creek
Road and on BLM Land in the Crown Mountain area.
Biological control:
Contact the Colorado Depai twent of Agriculture Insectary in Palisade for more information about
ongoing research into Biological Control for Dalmatian Toadflax.
Cultural control:
Good ground cover helps inhibit, but will not prevent, initial infestation. Re -seed disturbed areas
adjacent to toadflax infestations with competitive, native perennial grasses.
Mechanical control:
For small infestations, pulling toadflax by hand can be effective. Pull every year for 5-6 years to
deplete the reserves of the root system. Monitor the site for an additional 10-15 years to remove
seedlings produced from dormant seeds.
Chemical control:
Contact Pitkin County Land Management Depai truent for more specific information about herbicide
products, application rates, and equipment calibration.
HH. Dalmatian Toadflax (Linaria genistifolia) (continued)
Native Look-Alikes:
Dalmatian (and even Yellow) Toadflax is commonly confused with our native Golden Banner
(Thermopsis montana) which actually belongs to the Pea family. In fact, Golden Banner is also
commonly called "False Lupine," because its flowers very much resemble that of Lupine, which is
also a Pea.
Thermopsis is thus easily distinguished from the
noxious weed by its pea -like flowers, leaves,
and fruit:
• Leaves of Golden Banner are divided
into three leaflets, do not clasp the stem,
and lack the bluish tint of Dalmatian
Toadflax.
• Flowers of Golden Banner consist of the
distinctive banner, wings, and keel of the
Pea family; and lack the spur present on
Toadflax.
• Fruit of Golden Banner is a bean pod.
Thermopsis montana plant (left) and fruit (right)
II. Yellow Toadflax ("Butter and Eggs")
(Linaria vulgaris)
Key Characteristics:
Yellow toadflax is a member of the Snapdragon fam-
ily and is sometimes called common toadflax or but-
ter and eggs. It was introduced from Europe as an
ornamental and has now become a serious problem
to rangeland and mountain meadows. It is a perennial
reproducing from seed and from its extensive creep-
ing root system. Leaves are alternate and linear.
Flowers are yellow with an orange throat and
spurred. Yellow toadflax does well in all types of
soils up to 10,000 feet. Its displacement of desirable
grasses not only reduces ecological diversity, but
also reduces rangeland value and can lead to erosion
problems. Because of its early vigorous growth, ex-
tensive underground root system, and effective seed
dispersal, yellow toadflax is difficult to control.
Locations:
Yellow toadflax is common in Snowmass Village and the City of Aspen, especially along
the Roaring Fork River and atop Mountain, and along the Castle Creek and Frying Pan
drainages. It also occurs throughout the Crystal River Valley, including the very sensitive
Filoha Meadows area, where it grows in and among the exquisite native orchids and is
thus effectively impossible to eradicate without severely damaging important native diver-
sity. The number and extent of infestations throughout the County is alarming, as this is a
very difficult weed to kill, and success has been very limited.
Biological control:
Several species are currently in development at the Colorado Department of Agriculture
Insectary in Palisade. Contact them for more information.
Cultural control:
Maintain competitive communities of desirable species. Re -seed any open ground with na-
tive, perennial grasses to prevent invasion by yellow toadflax and other weed species.
Mechanical control:
Hand -pulling and digging are not recommended for control of Yellow Toadflax because it is
unlikely that the entire root system will be removed, and any root part left behind will fur-
ther the infestation. In cases of very small infestations of a handful of plants successful me-
chanical eradication may be possible. Tillage is also not recommended.
Chemical control:
Contact Pitkin County Land Management Depaitiiient for more specific information about
herbicide products, application rates, and equipment calibration.
6.32.06 Pitkin County Weed Watch List
A. Why a Weed Watch List?
The most critical tool for effective Weed Management is Prevention. The easiest weed to con-
trol is the one we don't have. Prevention requires vigilance, and vigilance requires awareness
of what is likely to be at our doorstep. For Pitkin County, this means being aware of what inva-
sions exist in neighboring counties. The Pitkin County Watch List consists of high -priority
weeds present in the neighboring counties of Garfield, Gunnison, and Eagle but not yet known
in Pitkin. With more information about what to look for and likely means of transport, we can
be ready to nip any new invasions in the proverbial (and literal) bud.
B. Japanese Knotweed
(Polygonum cuspidatum)
Key Characteristics
Japanese Knotweed is a member of the Buckwheat family, is native to Asia, and was originally im-
ported as an ornamental screen or hedge plant. It is a robust, bamboo -like perennial that spreads by
long creeping rhizomes to form dense thickets. It prefers moist areas like ditch- and streambanks.
It is a member of the Knotweed Complex, which also includes its hybrid, Bohemian Knotweed, and
the closely -related Giant Knotweed. Containment and control of these knotweeds is very difficult.
Although a major problem in other western states, such as Washington, and present in some areas in
Colorado, Japanese knotweed has not yet been included on the Colorado Noxious Weed List. It is
sometimes sold as Fallopia japonica (the Latin name for this plant in Europe and in Flora of North
America).
Stems are stout, cane -like, hollow between nodes, somewhat reddish -brown, 5 to 8 feet tall, and
branched. Stem nodes are swollen and surrounded by thin papery sheaths. Leaves are thick and
tough in texture, spade -shaped with a truncate base and an abruptly narrowed leaf -tip, 2 to 7 inches
long and about two-thirds as wide. Flowers are small, creamy -white to greenish -white, and grow in
showy plume -like, branched clusters from leaf axils near the ends of the stems.
Locations nearest Pitkin County
An infestation of Japanese Knotweed exists in El Jebel in Eagle County, along the ditch bank
between the Park -and -Ride and El Jebel Road.
Control Methods:
Contact the Pitkin County Land Management Office or the State Weed Coordinator to discuss
options for controlling Japanese and other invasive knotweeds.
C. Mediterranean Sage
(Salvia aethiopis)
Key Characteristics
Mediterranean Sage is a member of the
Mint family, and native to the Mediterra-
nean region and northern Africa. It has been designated as a
List A species by The Rules and thus must be eradicated from
the State of Colorado.
Mediterranean Sage grows erect from a stout taproot, living
as a biennial or short-lived perennial. First year rosettes are
blue-green and covered with woolly white hairs. Bolting in
the second year produces more leaves along a flowering stem
that can grow 2 to 3 feet tall and branches to resemble a can-
dalabra. This branching stem breaks off in the fall to become a
tumble weed that disperses many thousands of seeds (mature
plants can produce 100,000 seeds each). Leaves are woolly
and have a pungent odor when crushed. Flowers are white to
yellowish -white; the upper 2 petals form a lip resembling a
hooked beak; the lower 3 petals form 3 lobes, with outer lobes
larger than the central ones.
Locations nearest Pitkin County
Infestations of Mediterranean Sage exist in Garfield County
along I-70 corridor near the No Name Tunnel. This infestation
is particularly alarming because it exists in a high -traffic zone.
Biological Control
Biological Control is not an effective method of eradication. For this reason, Biological Control
agents are not included in the management plans prescribed by the State of Colorado for control of
List A species, which are mandated for eradication from Colorado.
Cultural Control
Report any suspected infestations of Mediterranean Sage to the Pitkin County Land Manage-
ment office! The key to effective control of this highly aggressive noxious weed is preventing its
establishment in the first place. Maintain healthy pastures and rangeland and continually moni-
tor your property for new infestations, especially near current known infestations, since tumbleweed
mobility of this plant can spread seeds far and wide. Do not purchase or plant this weed. Be
aware of what your local garden center is selling and report any noxious weeds for sale.
Mechanical Control
Hand pull or shovel when soil is moist. Make certain to pull up all the roots or sever at least 2 to 3
inches of taproot with a shovel. If plant is not yet in flower, shake excess soil from plant and turn
over to dry out. If plant is flowering, bag carefully so as not to scatter seeds which may be present.
Chemical Control
Contact the Pitkin County Land Management Department for more specific information about prod-
ucts, rates, and equipment calibration.
D. Purple Loosestrife
(Lythrum salicaria)
Key Characteristics
Purple Loosestrife is a member of the Loosestrife family, native to Europe,
and introduced to North America as an ornamental. It has since escaped
into natural areas, especially stream banks, shallow ponds, and wetlands,
where it quickly replaces the diverse and ecologically important plant com-
munity with a single monoculture. These stands have little habitat value for
wildlife, and can impede water flow in canals and ditches. It is a List A
weed in Colorado.
Purple Loosestrife reproduces primarily by seed, annually producing up to 3
million seeds which can remain viable in the soil for 5 to 20 years. Pieces
of root or stem can also produce new plants.
Stems are four-sided and grow 2 to eight feet tall. Leaves are 2-5 inches
long, lance -shaped, and occur in whorls. Flowers are tightly grouped in
long, vertical racemes that bloom from the bottom up from late June
through September; Blooms are pinkish -purple about one inch long, and
have five to seven petals;
Locations nearest Pitkin County
An Infestation of Purple Loosestrife exists in Eagle County on
private property near Rock Bottom Ranch.
Biological Control
Biological Control is not an effective method of eradication. For this rea-
son, Biological Control agents are not included in the management plans
prescribed by the State of Colorado for control of List A species, which are
mandated for eradication from Colorado.
Cultural Control
Report any suspected infestations of Purple Loosestrife to the Pitkin
County Land Management office! The key to effective control of this
highly aggressive noxious weed is preventing its establishment in the first
place. Do not purchase or plant this weed. Be aware of what your local
garden center is selling and report any noxious weeds for sale. Monitor
your property for invaders, especially in areas close to known infestations.
Mechanical Control
Hand removal of isolated individual plants can be effective on small infestations, but should be done
prior to seed set. It is important to remove the entire rootstalk to avoid re -growth from root frag-
ments. If the plant does flower, all flower heads should be carefully cut and bagged, even if chemi-
cal treatment is to be applied. This will prevent or reduce seed production.
Chemical Control
Contact the Pitkin County Land Management Department for more specific information about prod-
ucts, rates, and equipment calibration.
D. Purple Loosestrife (Lythrum salicaria) (continued)
Look-Alikes
Fireweed
(Chamerion angustifolium)
Purple Loosestrife is often confused with
native Fireweed at first sight, as the latter
has a similar shape and flower color (left).
However, where Loosestrife flowers have 5
-7 petals, Fireweed has only 4. Fireweed
flowers can be further distinguished by their
long styles terminating in four stigmas
(below).
Another distinctive feature of Fireweed is
its fruit. The long seed capsule splits open
in late summer to expose minute brown
seeds with long silky hairs (right).
A final rule of thumb is that, generally
speaking, Fireweed typically grows in drier,
open, sunny areas, while Purple Loosestrife
prefers wetland.
In addition to Fireweed, there are many alternatives to planting Purple Loosestrife that
are both better suited to Colorado and more beneficial to wildlife. These include:
Rocky Mtn. Penstemon
(Penstemon strictus)
Columbine
(Aqueligia sp.)
E. Orange Hawkweed
(Hieracium aurantiacum)
Key Characteristics
Orange Hawkweed belongs to the Sun-
flower family, is native to Europe, was
likely brought to North America as an or-
namental, and is now a List A Noxious
Weed in Colorado. With an incredible
capacity to propagate itself (underground
by rhizome and root bud and above
ground by runner and seed), Orange
Hawkweed quickly forms dense infesta-
tions, displacing native plants and domi-
nating sites as a solid mat of rosettes and
seedlings. It prefers moist sites such as
mountain meadows and woodlands, but
can also invade lawn, pasture and range.
Blooms are clusters of red -orange -yellow,
dandelion -like flowers with strap -shaped
petals notched at the tip. Leaves primar-
ily basal; sometimes one or two small
leaves along the stem. Stem and Leaves
bristly. Plant contains a milky juice.
Orange Hawkweed flower heads
are typically found in clusters.
sF '
Note the very bristly leaves and stem of Orange Hawkweed.
Locations nearest Pitkin County
Infestations of Orange Hawkweed have been treated in Gunnison County.
Biological Control
Biological Control is not an effective method of eradication. For this reason, Biological Control
agents are not included in the management plans prescribed by the State of Colorado for control of
List A species, which are mandated for eradication from Colorado.
Cultural Control
Report any sightings of Orange Hawkweed to the Pitkin County Land Management office!
The key to effective control of this highly aggressive noxious weed is preventing its establishment in
the first place. Do not purchase or plant this weed. Be aware of what your local garden center is
selling and report any noxious weeds for sale. Monitor your property for invaders, especially in ar-
eas close to known infestations.
Mechanical Control
Mechanical Control is NOT recommended for Orange Hawkweed, do to this weed's ability to repro-
duce bys stolons, rhizomes, and root fragments, which are typically stimulated or even further
spread via pulling, digging, and tillage.
Chemical Control
Contact the Pitkin County Land Management Department for more specific information about
products, rates, and equipment calibration.
E. Orange Hawkweed (Hieracium aurantiacum) (continued)
Look-Alikes
Orange Hawkweed closely resembles Yellow Hawkweed (Hieracium fendleri), which can be
distinguished by its yellow flowers. Our native Orange Agoseris (Agoseris aurantiaca) also
looks similar, but flowers are solitary and the leaves and stem are either smooth or have only a
few white hairs.
Yellow Hawkweed
(Hieracium fendleri)
Orange Agoseris
(Agoseris aurantiaca)
Monoculture of Orange Hawkweed.
F. Yellow Starthistle
(Centaurea solstitialis)
Key Characteristics
Yellow Starthistle is a member of the Sunflower family, is native to
Northern Spain, and now a List A Noxious Weed in Colorado.
Yellow Starthistle is a winter annual, meaning it typically germinates in
the fall, over -winters as a seedling, and forms its rosette in March -May,
bolting in Summer and flowering June -October. With optimal condi-
tions (-70°F and ample moisture), however, this weed can germinate in
16 hours or less, making it possible to produce multiple generations in a
single growing season. Yellow Starthistle is an incredible seed pro-
ducer — a single large plant can produce up to 100,000 seeds. Imagine
how fast even a small an infestation can grow in a single season!
Plants grow 1 to 4 inches tall from a vigorous taproot. Flowers are bright yellow and surrounded at
their base by sharp, stiff spines reaching 3/4 of an inch in length. Stems and leaves have a bluish -
green color. Basal leaves are 1-3 inches long and deeply lobed, while upper leaves are smaller and
narrower. Stems appear winged and both stem and leaves are covered with a slight whitish nap
(short cottony hairs). This plant is fatally poisonous to horses, causing Chewing Disease.
Locations nearest Pitkin County
An extensive infestation of Yellow Thistle exists near Paonia in Delta County.
Biological Control
Biological Control is not an effective method of eradication. For this reason, Biological Control
agents are not included in the management plans prescribed by the State of Colorado for control of
List A species, which are mandated for eradication from Colorado. However, Insects are available
for control of Yellow Starthistle. Contact the Colorado Department of Agriculture Insectary in Pali-
sade for more information.
Cultural Control
Report any sightings of Orange Hawkweed to the Pitkin County Land Management office!
The keys to effective control of this highly aggressive noxious weed are prevention of seed -set in
existing populations, frequent scouting for new infestations, rapid treatment of newly discovered
infestations, and prevention of introduction of this weed to new areas. Do not purchase hay,
straw, seed, or soil from areas known to be infested with Yellow Starthistle.
Mechanical Control
Hand -pull when soil is moist, making sure to pull out all the roots. Bag carefully to prevent seed -
scatter if flowering, and be sure to include dried skeletons as these may still contain seed. Plants
vary greatly in size so be sure to look for plants that are only a few inches tall, as well as plants that
are several feet tall. Mowing is NOT recommended, as it can extend the life of the plant and stimu-
late additional flowering, lower to the ground.
Chemical Control
Contact the Pitkin County Land Management Department for more specific information about
products, rates, and equipment calibration.
E Yellow Starthistle (Centaurea solstitialis) (continued)
Look-Alikes
There are several common native and non-native (but non -noxious) plants that can be mistaken
for Yellow Starthistle. These include the non-native Western Salsify (Tragopogon dubius) and
Safflower (Carthamus tinctorius), and the native Curlycup Gumweed (Grindelia squarrosa)
and Buffalo Bur (Solanum rostratum).
N
A
T
I
V
E
Western Salsify
(Tragopogon dubius)
• Dandelion -like flower
• Bracts not thorns — they are soft
• Leaves and stem have milky latex
• Leaves linear, strap -shaped
Buffalo Bur
(Solanum rostratum)
• Flower has five broad petals
• Entire plant covered in sharp spines
(not just directly below flower)
• Leaves dark green, large, deeply lobed
Safflower
(Carthamus tinctorius)
• Annual oilseed/die crop
• Large, broad, spine -edged bracts rather than
slender spines only
• Overall more branched than Starthistle
Curlycup Gumweed
(Grindelia squarrosa)
• Biennial or short-lived perennial
• No spines; bracts curl backward and are
very sticky, with a strong medicinal scent
• Leaves toothed
6.32.070. Early Detection, Rapid Response
A. The EDRR Approach
Pitkin County has adopted a philosophy of "Early Detection, Rapid Response" (EDRR).
Early detection is the swift identification and documentation of weed species newly
introduced (or newly discovered) in an area. Rapid Response is the immediate follow-up
treatment, outreach, and prevention to eradicate the infestation and avoid re -introduction.
EDRR can stop the spread of new and emerging invasive plant species before they become
established. It is one of the most cost-effective and ecologically viable methods for
controlling invasive weeds.
Pitkin County's approach to weed management is modeled off the EDRR program
administered by the Colorado Department of Agriculture. The goals of the State EDRR
program are to:
• provide alert lists, identification resources, and reporting protocols for targeted
plant pest species
• build an invasive plant network that incorporates professionals and outdoor
enthusiasts alike throughout Colorado to detect new and emerging species in our
state
• provide information and planning assistance to rapidly respond to and
successfully manage newly detected species.
Crucial to the success of EDRR is a clear understanding of the jurisdictional break -down
of an area. Knowing who is responsible for enforcement and who for treatment makes
for more efficient reporting, documentation, elimination, and monitoring of new
infestations. According to the Act:
It is the duty of all persons to use integrated methods to manage noxious weeds if
the same are likely to be materially damaging to the land of neighboring
landowners. (C.R.S. 35-5.5-104)
Here, "persons" are defined as:
an individual, partnership, corporation, association, or federal, state, or local
government or agency thereof owning, occupying, or controlling any land,
easement, or right-of-way, including any city, county, state, or federally owned
and controlled highway, drainage, or irrigation ditch, spoil bank, borrow pit, gas
and oil pipeline, high voltage electrical transmission line, or right-of-way for a
canal or lateral.
Because different entities manage different areas and different assets in Pitkin County, be
they public or private, the responsible "persons" will vary depending on the location(s) of
the weed or infestation in question. This can get confusing. The following section
outlines the jurisdictional divisions of Pitkin County, lists the typical weed species
present in each, and describes new or otherwise alarming weed infestations.
B. Jurisdictional Overview of Pitkin County
1. Private Property
The private landowners are ultimately responsible for ensuring that their property
complies with applicable laws, including the Act, the Rules, and this Plan. This includes
lands held by a corporation or other such entity. These laws outline the enforcement
authority of the local governing body (e.g. municipality or county), should the property in
question not be in compliance.
It is important for private landowners and their neighbors to be educated and vigilant
about noxious weeds, especially with regard to new or rare weeds in Pitkin County. This
will increase the likelihood of discovery of new outbreaks before they become
widespread. Especially important weeds to watch for on private property in Pitkin
County include:
• Absinth Wormwood (Artemisia absinthium)
o Invasive Ornamental
o Known infestations in Pitkin County exist in the AABC and North Forty
neighborhoods, on Red Mountain, in Old Town Basalt, along Thompson
Creek, Maroon Creek, and Capital Creek Roads, and along Hwy 133 near
the Garfield-Pitkin County Line and near Marble.
• Dame's Rocket (Hesperis matronalis)
o Invasive Ornamental
o Rare state-wide
o Found on private and public property throughout Pitkin County, especially
in Snowmass Village and Aspen.
• Sulfur Cinquefoil (Potentilla recta)
o Known infestations exist near lower Brush Creek Road, on the Child
Ranch on upper Capitol Creek, and at Filoha Meadows in the Crystal
River Valley.
• Meadow Knapweed (Centaurea pratensis)
o Invasive Ornamental
o Known to exist in Little Elk Creek Village
• Salt Cedar (Tamarix chinensis; T. ramosissima)
o Known infestation treated in 2009 at Wingo
o Infestation along the Crystal River by Penny Hot Springs believed to have
been eradicated
• Cypress Spurge (Euphorbia cyparissias)
o Invasive Ornamental
o Known to exist on a few properties on lower Snowmass Creek Rd.
• Myrtle Spurge (Euphorbia myrsinites)
o Invasive Ornamental
o Known to exist on Red Mountain and on scattered properties in Brush
Creek Village, Snowmass Village, Basalt, Emma, and the Crystal River
Valley.
o Heavy infestations exist in Glenwood Springs.
• Dalmatian Toadflax (Linaria genistifolia)
o Invasive Ornamental
o Common in Garfield County, rare in Pitkin.
o Found in on upper Capitol Creek and upper Snowmass Creek roads, and in
the Redstone area.
These weeds are rare in Pitkin County overall, should not be planted or sold, and must be
eradicated when found. Early and persistent enforcement of applicable laws on private
property is crucial for keeping these weeds from becoming widespread in Pitkin County.
2. Municipalities
a. City of Aspen
Responsibility for noxious weed management within the City of Aspen (COA) falls
under the jurisdiction of the Aspen Parks Department. The Parks Department has had
a treatment program in place since 1995 on its Parks and Open Space and Trails
lands. The Department has also been increasing enforcement efforts on private
properties within the city limits Escaped ornamentals are a big problem in Aspen,
especially the following:
• Absinth Wormwood (Artemisia absinthium)
• Scentless Chamomile (Matricaria perforata)
• Dame's Rocket (Hesperis matricaria)
• Oxeye Daisy (Chrysanthemum leucanthemum)
• Myrtle Spurge (Euphorbia myrsinites)
• Common Tansy (Tanacetum vulgare)
• Yellow Toadflax (Linaria vulgaris)
For more information on the City of Aspen Noxious Weed Program, contact Chris
Forman, City of Aspen Forester, at chrisf@ci.aspen.co.us or 970-429-2026.
b. Town of Snowmass Village
The Town of Snowmass Village (TOSV) Public Works department coordinates
noxious weed programs within the town limits. Currently, weed management
activities are contracted annually to a commercial herbicide application company,
overseen by the Town Landscape Foreman. Town Staff have increased enforcement
efforts on infested private properties in recent years. Common weed species in TOSV
are:
• Scentless Chamomile (Matricaria perforata)
• Oxeye Daisy (Chrysanthemum leucanthemum)
• Poison Hemlock (Conium maculatum)
• Common Tansy (Tanacetum vulgare)
• Canada Thistle (Cirsium arvense)
• Plumeless Thistle (Carduus acanthoides)
In 2008, TOSV and County and Town staff released the Defoliating Hemlock Moth
(Agonopterix alstroemeriana) on two infestations of Poison Hemlock on upper Brush
Creek. They seemed to have an effect in their first season, and should be monitored
to see if the insect population continues to reproduce and over -winter.
Several new noxious weed species have begun popping up in patches around Town in
recent years. These include:
• Chicory (Cichorium intybus)
• Hoary Cress (Cardaria draba)
• Spotted Knapweed (Centaurea maculosa)
• Russian Knapweed (Acroptilon repens)
• Diffuse Knapweed (Centaurea diffusa)
• Myrtle Spurge (Euphorbia myrsinites)
• Yellow Toadflax (Linaria vulgaris)
Treatment and close monitoring of these infestations should continue to prevent them
from spreading to new areas or growing to large to control. Monitoring and
enforcement at the new base village and other highly disturbed areas, as well as
enforcement of re -vegetation requirements, should remain a priority.
For more information on the Town of Snowmass Village Noxious Weed Program,
contact Pam Mulleavey, Town of Snowmass Village Landscape Foreman, at
pmulleavey@tosv.com or 970-923-5110 x 303.
c. Town of Basalt
The Town of Basalt (TOB) lies in both Pitkin and Eagle counties. It is recommended
that Basalt adopt both counties' noxious weed lists. Most noxious weed issues are
addressed by the Town's Public Works Department. In the past, the TOB has taken a
primarily mechanical approach to weed control, with varied success. The most
common weeds in Basalt are:
• Oxeye Daisy (Chrysanthemum leucanthemum)
• Common Tansy (Tanacetum vulgare)
• Canada Thistle (Cirsium arvense)
• Musk Thistle (Carddus nutans)
• Plumeless Thistle (Carduus acanthoides)
Alarming new or rare infestations in the TOB include:
• Absinth Wormwood (Artemisia absinthium)
• Leafy Spurge (Euphorbia esula)
• Myrtle Spurge (Euphobia myrsinites)
• Dame's Rocket (Hespers matricaria)
These weeds are highly invasive and difficult to control without herbicide once
established. Elimination of these species should be a high priority.
For more information on the Town of Basalt Noxious Weed Program, contact Lisa
DiNardo, Town of Basalt Horticulturist/Certified Arborist, at basaltgardens@basalt.net or
970-927-4723 x 404.
3. County Lands
Pitkin County is responsible for treatment of weeds on its properties, and has
enforcement authority over private property in the unincorporated portions of the County.
County properties can be categorized as follows: Rights -of -Way, Airport, Solid Waste
Center, Open Space and Trails, General Fund parcels, and Grounds.
a. Rights -of -Way
Pitkin County maintains about 300 miles of County roads and rights -of -way (ROW).
The BOCC adopts an official Pitkin County Road List showing all roads that have
been incorporated into the County road system. This list is updated to reflect
additions, deletions, and alterations. The current road list can be found in the most
recent version of the Pitkin County Asset Management Plan (AMP), available from
the Pitkin County Public Works Office, or online at:
http: //www. aspenpitkin. com/Portals/0/docs/county/PublicWorks/2006AMPfinal.pdf.
This list includes US Forest Service roads which are maintained by Pitkin County at
the direction of the Forest Service. It also includes roads for which special
circumstances, such as additional road maintenance agreements and settlements,
exist. Such special agreements include Intergovernmental Agreements, Contracts
with private individuals/companies, and Special road maintenance agreements. These
agreements may redirect responsibility for ROW vegetation maintenance to another
entity, such as the local metro district or HOA. For more information about the road
list and these agreements, contact the Pitkin County Land Management Office.
Unlike for such maintenance activities as snow -plowing and surface improvements,
the level of Noxious Weed Maintenance on County ROW is dictated by the extent
and type of infestation present, rather than by the AMP -designated Service Level.
ROW treatment starts every year at lower elevations in the County where the growing
season starts earlier (generally speaking, in the northwestern portion of the County).
Treatment typically begins in these areas in late April or early May. Each County -
maintained right-of-way is aimed to be treated a minimum of once per year. Heavily
traveled and heavily infested ROW, and ROW containing high -priority weeds or
weeds that require special control measures, may be treated a second and possibly a
third time, in order to meet State and local management objectives.
It has been the County's philosophy to minimize the use of herbicides, and thus the
impacts on desirable vegetation, and maximize treatment efficiency by selectively
spot treating noxious weeds with a handgun attached to a truck -mounted, pressurized
spray unit. There will be no general herbicide applications on County ROW to weeds
not listed in this WMP, unless specifically requested by the County Transportation
Department or the BOCC to improve sight and safety conditions.
b. Airport
The Airport consists of about 250 acres of treatable land and has undergone extensive
expansion since 2002. Because of this widespread soil disturbance, significant weed
control is required. The primary weeds at the airport are:
• Scentless Chamomile (Matricaria perforata)
• Houndstongue (Cynoglossum officinale)
• Canada Thistle (Cirsium arvense)
• Plumeless Thistle (Carduus acanthoides)
• Oxeye Daisy (Chrysanthemum leucanthemum)
Other rarer weeds to watch for and eradicate at the Airport include:
• Absinth Wormwood (Artemisia absinthium)
• Black Henbane (Hyoscyamus niger)
• Sulfur Cinquefoil (Potentilla recta)
• Russian Knapweed (Acroptilon repens)
• Leafy Spurge (Euphorbia esula)
• Bull Thistle (Cirsium vulgare)
c. Solid Waste Center
The Solid Waste Center (SWC) consists of about 45 acres, with about 20 acres of
treatable land. This area continues to be a priority for weed treatment as it is a center
of activity, in terms of both traffic volume and dissemination of materials. The
primary weeds at the SWC are:
• Scentless Chamomile (Matricara perforata)
• Leafy Spurge (Euphorbia esula)
• Canada Thistle (Cirsium arvense)
• Plumeless Thistle (Carduus acanthoides)
Because materials and traffic from all over the region come to the SWC, any weed
species could hitch -hike in and be again dispersed elsewhere. For this reason, it is
important to maintain diligent and effective weed control at the SWC.
d. Open Space and Trails
The Pitkin County Open Space and Trails (OST) program includes over 2000 acres of
property. In terms of management objectives and methods, this WMP does not make
a distinction between lands managed by Pitkin County Land Management and those
managed by OST. For specific management goals of OST properties, please contact
the OST Land Steward at garyt@co.pitkin.co.us or 970-920-5355.
e. General Fund Parcels
Pitkin County owns many parcels which are simply owned by the General Fund,
rather than any of the above entities. These parcels are scattered throughout the
County including the Redstone Coke Ovens area, two parcels on Shield 0 Mesa, and
some land adjacent to the Rio Grande Trail in Woody Creek near River Woods Road.
These properties can be located using the Pitkin County Geographic Information
System Mapping Online (GISMO) at http://www.aspenpitkin.com/GISMO. Weeds
present vary with location, but typical weeds include:
• Field Bindweed (Convolvulus arvensis)
• Scentless Chamomile (Matricaria perforata)
• Houndstongue (Cynoglossum officianale)
• Common Mullein (Verbascum thapsus)
• Canada Thistle (Cirsium arvense)
• Musk Thistle (Carduus nutans)
• Plumeless Thistle (Carddus acanthoides)
Generally speaking, the closer these parcels are to the backcountry, the higher priority
the infestations, regardless of the weeds present. This is in addition to the priorities
and management objectives set by The Rules and set forth in this WMP.
f. Grounds
The Buildings and Grounds Maintenance Department (BGM) manages the grounds
around County buildings. In terms of management objectives and methods, this
WMP does not make a distinction between lands managed by Pitkin County Land
Management and those managed by BGM. For specific management goals and
techniques of BGM properties, please contact the Groundskeeper at 970-618-9964.
4. State Lands
a. Colorado Department of Transportation
Since 1991, Pitkin County has held an Intergovernmental Agreement with the
Colorado Department of Transportation (CDOT) to treat noxious weeds on Highway
82 and Highway 133 ROW. This agreement is renewed on an annual basis for the
control of weeds on the CDA Noxious Weed List.
SH-82
There are 55 miles of State Highway 82 (SH-82) ROW in Pitkin County, which are
estimated to be 10% infested. This is a reduction from the estimates of the 1987
Pitkin County Weed Control Manual, which put the infested percentage at 50%. The
major weeds on Hwy 82 are:
• Field Bindweed (Convolvulus arvensis)
• Scentless Chamomile (Matricaria perforata)
• Downy Brome (Bromus tectorum)
• Houndstongue (Cynoglossum officinale)
• Common Mullein (Verbascum thapsus)
• Oxeye Daisy (Chrysanthemum leucanthemum)
• Common Tansy (Tanacetum vulgare)
• Canada Thistle (Cirsium arvense)
• Plumeless Thistle (Carduus acanthoides)
East of Aspen on SH-82, the following weeds are of special concern:
• Dame's Rocket (Hesperis matronalis)
• Russian Knapweed (Acroptilon repens)
• Spotted Knapweed (Centaurea maculosa)
• Yellow Toadflax (Linaria vulgaris)
In Snowmass Canyon and points near Emma, Perennial Pepperweed (Lepidium
latifolium) has established itself and has proven difficult to eradicate. It is vital that
this tenacious weed is at a minimum eliminated seasonally before it sets seed, in order
to prevent it from spreading to new areas of the County.
Other rare weeds that have been found in patches at various points along SH-82:
• Absinth Wormwood (Artemisia absinthium)
• Black Henbane (Hyoscyamus niger)
• Diffuse Knapweed (Centaurea diffusa)
• Russian Knapweed (Acroptilon repens)
• Spotted Knapweed (Centaurea maculosa)
• Leafy Spurge (Euphorbia esula)
• Bull Thistle (Cirsium vulgare)
• Scotch Thistle (Onopordum acanthium, O. tauricum)
SH-133
The 20 miles of State Highway 133 (SH-133) ROW in Pitkin County are estimated to
be 10% infested. This is a decrease of 5% since 2006. The primary weeds are:
• Scentless Chamomile (Matricaria perforata)
• Musk Thistle (Carduus nutans)
• Yellow Toadflax (Linaria vulgaris)
Oxeye Daisy (Chrysanthemum leucanthemum) has become a growing concern in the
Crystal River Watershed, on both public ROW and private property. Enforcement
and Education should be a priority in this region of the County, to prevent Oxeye
from dominating critical wetland and riparian habitat and further disturbing
agricultural lands.
In addition, the following weeds are present in patches and less common:
• Absinth Wormwood (Artemisia absinthium)
• Hoary Cress (Cardaria draba)
• Plumeless Thistle (Carduus acanthoides)
• Common Tansy (Tanacetum vulgare)
• Russian Knapweed (Acroptilon repens)
• Dalmatian Toadflax (Linaria genistifolia)
b. Colorado Department of Natural Resources State Land Board
The Colorado State Land Board owns approximately 475 acres of land which
comprise most of Williams Hill between Watson Divide and Old Snowmass.
5. Federal Lands
a. White River National Forest
The United States Forest Service has extensively mapped and inventoried its land in
Pitkin County, and mapping and treatment of List A and high -priority List B species
is ongoing. For more information contact Wayne Ives, Range Technician, White
River National Forest Sopris Ranger District at 970-963-2266 or WIves@fs.fed.us.
b. Bureau of Land Management
In 2008, the Bureau of Land Management (BLM) completed a weed inventory on all
disturbed areas on BLM Land in Pitkin County. These areas included roads, range
improvements, trails, trail heads, campsites, and drainages. The agency is continuing
to treat infestations of Plumeless Thistle, Canada Thistle, and Houndstongue on its
lands in the Prince Creek Drainage and Crown Mountain areas of Pitkin County. In
2009 several new infestations of Dalmatian Toadflax were found on Crown
Mountain. For more information contact Dereck Wilson, Rangeland Management
Specialist for the BLM, at 970-876-9070 or Dereck Wilson@blm.gov.
C. Cooperative Weed Management Areas
Another important tool in any EDRR program is the establishment of Cooperative Weed
Management Areas (CWMAs) to coordinate Weed Management efforts regionally. The
National Network of Invasive Plant Centers (NNIPC) defines Cooperative Weed
Management Area as a "partnership of federal, state, and local government agencies,
tribes, individuals, and various interested groups that manage noxious weeds or invasive
plants in a defined area." The following description is taken from the NNIPC website at:
www.invasiveplantcenters.org/cwmas.html:
CWMAs often function under the authority of a mutually developed
Memorandum of Understanding or Cooperative Agreement and are governed by a
steering committee. Together, CWMA partners develop a comprehensive weed
management plan for their area. At the least, CWMA plans include weed
surveying and mapping components as well as plans for integrated weed
management. More comprehensive plans may include education and training,
early detection of new invaders, monitoring, revegetation, and annual evaluation
and adaptation of the weed management plan.
Five characteristics of a CWMA:
• Defined geographical area distinguished by a common geography, weed
problem, community, climate, political boundary, or land use.
• Involvement or representation of the majority of landowners and natural
resource managers in the defined area
• Steering committee
• Commitment to cooperation
• Comprehensive plan that addresses the management or prevention of one
or more noxious weeds or invasive plants.
The establishment of CWMAs in Pitkin County will be an important tool in the
further prevention and management of new weed species, as well as in the protection
of "weed -free" zones.
6.32.080 Enforcement
A. Statutory Enforcement Provisions Govern
The Colorado Noxious Weed Act, § 35-5.5-101, C.R.S. (2009), et seq., (hereinafter the
Act) states that certain invasive weeds pose a threat to the continued economic and
environmental value of the land in Colorado; designates these weeds as "noxious" in
Colorado; and mandates their management by all landowners in the State. The Act contains
specific provisions empowering the County to enforce its terms, including without limitation
§§ 35-5.5-108.5, -109, and -110. This WMP shall be enforced in accordance with those
statutory provisions and any other applicable laws. A flow chart that generally illustrates the
sequence of enforcement activities currently set forth in the Act is appended hereto; this flow
chart is provided for illustrative purposes only, and does not supersede the provisions of the
Act. Users of this WMP are advised to consult the language of the Act itself, as its terms will
control over any inconsistency that may be depicted in the flow chart.
B. Noxious Weeds Declared a Public Nuisance
The noxious weeds listed in Section 3 of this WMP, at any and all stages, are subject to
all the laws and remedies relating to the prevention and abatement of nuisances, including,
but not limited to, those set forth in the Act.
C. Authorized Agents for Enforcement
Pursuant to §35-5.5-105(2), C.R.S., The Pitkin County Land Manager, the Pitkin County
Code Enforcement Officer, the Pitkin County Sheriff and their respective designees are
hereby designated as "authorized agents," empowered to enforce the Act and this NWMEP in
unincorporated Pitkin County, by utilizing those procedures set forth in §35-5.5-108,-108.5,
-109, C.R.S and any other applicable local, State and Federal statutes, rules, regulations, and
ordinances, including the remaining provisions of this Section.
D. Enforcement Flowchart
Full Extent of Infestation
Identified by County Agent from:
• public land/right-of-way
• neighboring parcel
•
Inspection requested by:
1. Landowner
2. Neighbor
3. County Agent
Pitkin County verifies that any adjacent County lands are in compliance
with WMP and State Weed Law.
1
Pitkin County notifies landowner of pending inspection via certified mail.
Landowner has ten (10) days to respond.
1
Landowner responds within 10 days
and permits inspection?
Inspection occurs.
Noxious Weeds identified.
NO
4
Inspection warrant obtained
from County Court.
Presence of List A or List B species with mandated for Eradication?
YES (§ 35-5.5-108.5)
1
Certified Mail sent to Landowner that:
• names noxious weeds present and the
management objective for each
• requires landowner to commence
eradication efforts within specified
period/condition
• names integrated weed management
techniques prescribed for Eradication
Landowner has 5 days from postmark to comply
or submit an acceptable plan and schedule.
NO 035-5.5-109)
1
Certified Mail sent to Landowner that:
names noxious weeds present
advises landowner to manage weeds
names best available control methods of
integrated management.
Landowner has no more than 10 days to:
1. comply;
2. submit plan and schedule; OR
3. request arbitration panel determine plan
Landowner complies on time?
Landowner complies on time?
YES
Pitkin County follows up on -site to
verify completion of management.
Management found to be satisfactory?
YES
NO
NO
1
Two Enforcement Options:
1. After a 10 day notice for a public
hearing the BOCC may declare the
property a public nuisance and ensue
with all the laws and remedies relating
to the prevention and abatement of
nuisances, including, but not limited
to, those set forth in §35-5.5-108,-
108.5,-109, and -110, C.R.S.
2. Pitkin County may force
management of the weed problem
following a duly noticed public
hearing (10 days). The landowner will
be responsible for all costs associated
with management including a 20%
administration surcharge. These fees
will be assessed as a lien against the
property.
NO
Landowner submits acceptable
plan and schedule on time?
NO
Landowner requests arbitration
panel within 10 days?
YES
Pitkin County selects
arbitration panel consisting of:
• a weed management
specialist or weed
scientist
• a landowner of similar
land in the same county
• a third member chosen by
the first two
Landowner may challenge
any one member of the panel,
who will be replaced by new
member from same category.
The panel's decision is final.
Landowner implements plan.
Pitkin County follows -up once
scheduled work is complete.
Enforcement Actions Complete!
Follow-up in following seasons.
6.32.090. Priorities and Goals
A. Priorities
1. Outreach, Education, and Training
Outreach and Education are pivotal to the sustained success of this WMP. Most weed
species, if detected early, can be eradicated before they become established. It is
important that the public is able to identify noxious weeds and is aware of and committed
to the necessity of rapid response to new infestations. In addition, it is important that all
land managers — be they public or private — are trained in Best Management Practices, in
order to maximize efficiency and effectiveness of treatments while minimizing
environmental impact.
Groups targeted for noxious weed education include those with agricultural interests,
homeowners associations, the green industry, developers, recreational groups,
environmental and open space land management non-profit organizations, youth groups,
and schools. This instruction will be coordinated by the Land Management department in
cooperation with the Weed Advisory Board.
2. Integrated Control
Carry out weed control practices on Pitkin County owned lands and rights -of -way.
3. Surveying and Mapping
In a continuing effort to manage noxious weeds with sound strategy, existing noxious
weed inventories will be compared to new mapping data. These data will encompass
County, State, and Federal properties, as well as major rights -of -way that are not County -
maintained and private lands. Private lands will be included after written permission has
been granted by the owner and occupant.
4. Intergovernmental Agreements
Formal cooperative agreements will be sought and maintained between Pitkin County,
Federal and State landowners, and local governments, to facilitate a coordinated regional
effort in managing the noxious weeds listed in this WMP.
5. Partnerships
Partnerships with environmental non-profit organizations and private landowners will
also be sought. Such partnerships may include: Cooperative Weed Management Areas,
Watershed -scale management projects, Natural Resources Conservation Service
Environmental Quality Incentives Program (NRCS EQIP) grant projects, and cost sharing
programs.
6. Prevention and Early Detection
It will be a distinct priority of the Land Management department both to prevent the
establishment of new noxious weeds, and to manage existing infestations to prevent them
from spreading into previously un-infested areas. Prevention will include the attachment
of strict revegetation requirements to County -issued permits for projects causing land
disturbance, as well as a commitment to prompt revegetation of disturbance on County
properties and ROW.
B. Goals
1. Short Term Goals
• Continue managing existing infested acreage aggressively to prevent spread and
reduce population density.
• Implement control activities for noxious weed species that are new to the County
through education and rapid response.
• Encourage the implementation of noxious weed control activities on all infested
acreage within the district.
• Increase awareness of The Act (C.R.S. § 35-5.5-101 et seq.) and The Rules (8
CCR 1206-2).
• Coordinate the formation of Cooperative Weed Management Areas.
• Develop a cooperative spirit within County departments that encourages
prevention of noxious weeds through pro -active planning efforts.
• Continue and expand the use of biological control releases throughout the area,
where appropriate.
• Survey County and (where permission granted) Private land holdings for noxious
weeds and record digitally for use in Noxious Weed GIS data layer.
• Meet the State mandate of Eradication of:
o Absinth Wormwood (Artemisia absinthium)
o Black Henbane (Hyoscyamus niger)
o Chinese Clematis (Clematis orientalis)
o Salt Cedar (Tamarix chinensis; T. ramosissima)
o Diffuse Knapweed (Centaura diffusa)
o Spotted Knapweed (Centaurea maculosa)
o Perennial Pepperweed (Lepidium latifolium)
o Dalmatian Toadflax (Linaria genistifolia)
o Plumeless Thistle (Carduus acanthoides)
(only in the Crystal River Watershed)
and the State mandate of Containment of:
o Sulfur Cinquefoil (Potentilla recta)
to the area demarcated by the northern border of Pitkin County, Longitude
106° 56'17" W, Longitude 39° 14'59" N, and Latitude 107° 3'48" W. For
all land within these boundaries, suppression is the specified State
management objective (see Figure 1).
o Hoary Cress (Cardaria draba)
to the area demarcated by the northern border of Pitkin County, Longitude
106° 48'46" W, Latitude 39° 11'15" N, and Longitude 107° 7'33" W. For
all land within these boundaries, suppression is the specified State
management objective (see Figure 2).
o Russian Knapweed (Acroptilon repens)
to the area demarcated by the northern border of Pitkin County, Longitude
106° 48'45" W, Latitude 39° 11' 14" N, and Longitude 107° 3'44" W. For
all land within these boundaries, suppression is the specified State
management objective (see Figure 3).
o Leafy Spurge (Euphorbia esula)
to the area demarcated by the northern border of Pitkin County, Longitude
106°45' 1" W, Latitude 39°9'57" N, Capitol Creek, and State Highway 82.
For all land within these boundaries, suppression is the specified State
management objective (see Figure 4).
2. Long Term Goals
• Update the existing Noxious Weeds GIS layer and distribute population
information through the Pitkin County website.
• Further develop and implement revegetation guidelines in cooperation with other
district entities.
• Maintain relationships with municipal authorities to put into practice a
comprehensive weed management program for all lands within the boundary of
the district.
• Maintain agreements with federal agencies, state agencies, and local governing
bodies to maximize effectiveness of weed management efforts.
• Maintain agreements and contracts with non -governmental organizations
interested in environmental protection with regard to noxious weed management.
• Federal, State, Municipal, County, and private land holdings' noxious weed
survey data to the Pitkin County Noxious Weeds GIS layer.
C. Figures
1. Sulfur Cinquefoil Containment Map
Sulfur cinquefoil Potenteo recta Figure 184
Pitkin County
2. Hoary Cress Containment Map
Hoary cress Cardarra draba
Pitkin County
Figure 163
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Firkin County
Figure 178
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Pitkin County
Snowmass
Elimination
Completed In 2011
Suppression
edstone
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Figure 138
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6.32.100. Additional Requirements
Pitkin County requires disturbed areas to be re -vegetated and properly maintained after
development activities, in order to prevent new noxious weed infestations from taking hold.
These requirements are typically included in the application process for Right -of -Way, Access,
and Earthmoving permits and for Land Use applications. Details for such requirements can be
found in the Land Use Code and Asset Management Plan, both available online at:
www.aspenpitkin.com/Departments/County-Code/
Appendix A
The Threat of Escaped Ornamentals
Most plants used for landscaping purposes lack the ability to proliferate outside of the
cultivated environment of the home garden. Yet certain exotic plants and seeds were imported
to the United States for their aggressive growth habits, xeriscape potential, or re -seeding
capabilities. Many of these plants have escaped cultivation and become aggressive invaders of
wildlands. Known as Escaped Ornamentals or Invasive Ornamentals, these plants include
(among others) Dame's Rocket (Hesperis matronalis), Common Tansy (Tanacetum vulgare),
Mediterranean Sage (Salvia aethiopis), Oxeye Daisy (Chrysanthemum leucanthemum), Purple
Loosestrife (Lythrum salicaria), Scentless Chamomile (Matricaria perforate) and Yellow
Toadflax (Linaria vulgaris).
The very aggressive growth traits which make these plants desirable for a garden or landscape
may also enable them to thrive outside cultivated areas and become fierce competitors with our
native vegetation. Because they exist here without the presence of sufficient environmental
controls or natural predators, these plants have the ability to spread extensively and pose a
severe threat to the delicate balance of our native ecosystems.
Since various invasive ornamental plants are attractive and establish themselves quickly, they
are popular with landscapers and gardeners and may even be purchased through certain
nurseries in the Roaring Fork Valley. It is imperative that we educate landscape architects,
gardeners, and nursery growers about the need to eliminate such plants from their landscape
plans. Otherwise, these plants will inevitably escape from the cultivated garden and jeopardize
the natural wildflower and plant communities that we cherish. Native wildflowers such as
Colorado Blue Columbine, our state flower, cannot compete with aggressive, invasive
ornamental plants for nutrients, sunlight, and water. As a result, our biologically diverse
mountain meadows, grasslands, and wetlands are in danger of being overrun by monocultures
of non-native species.
Native stand of wildflowers with a small
population of oxeye daisy.
Same site two years later
Appendix B
Native Thistles in Pitkin County
You've learned about how bad some thistles can be for our environment. You're primed and
ready to pull or spray. Good for you! But before you target all thistles, remember that there are
20 native thistle species in Colorado, and these play an important role for wildlife. Native
thistles should not be killed, because they are not noxious weeds.
How do you tell a native thistle from a noxious thistle?
While there is no steadfast rule to determining native thistles from noxious ones (other than
actual identification!), there are some general guidelines:
• If the stand of thistles is very dense or very tall (6+ feet), it is usually noxious.
• If you are above timberline and see a thistle, it is probably native.
• Native thistles tend to be shorter than non-native ones, and are often found as individual
plants or in very small groups of 2-4 plants.
• A thistle with a white or yellow flower (the FLOWER, not the fluffy dandelion -like
seeds), is probably native. An exception is Yellow Starthistle, which is a VERY
invasive Noxious Weed!
Here are a few common native thistles in Pitkin County
American Thistle
Cirsium centaurae
American thistle is a perennial,
growing to 3 feet tall, in colonies, with
erect, reddish, cobwebby stems.
Flowering time is June to August.
Flower heads are 1 1/2 inches high,
without ray flowers. Disk flowers are
white to tan -colored, with purple
stripes; bracts are spine -tipped, with
lattice -like hairs. Leaves are deeply
incised, whitish and hairy beneath, and
spiny. Note reddish stem and whitish
brown flowers for distinction from
noxious thistles.
American thistles are commonly found
in ravines and forest openings, and on
rocky slopes and banks.
Frosty Ball Thistle
Cirsium scopularum
Frosty Ball Thistle is a perennial
growing to 2 feet tall. The flowers are
perfect (have both male and female
organs) and are pollinated by bees, flies,
moths, butterflies, and beetles. The
plant prefers light (sandy), medium
(loamy) and heavy (clay) soils. The
plant prefers acid, neutral and basic
(alkaline) soils. It cannot grow in the
shade. It requires moist soil.
Look for Frosty Ball Thistle in sunny
areas in meadows, slopes, and along
roadways or trails. There are
populations on Independence Pass.
Meadow Thistle or Elk Thistle
Cirsium scariousum
This is a fairly easy thistle to identify,
because it is frequently found without a
stem. When present, stems are generally
very short and thick, with the flower
heads sessile. Flowers are white to a pale
pink -purple. The leaves are spiny, but
entire to somewhat scalloped. This plant
flowers from June into August.
True to its name, Meadow Thistle grows
in meadows and other moist places from
the foothills to 10,500 feet.
Creamy Thistle or Prairie Thistle
Cirsium canescens
Creamy thistle is a perennial growing to
3 feet tall, with a stout, branched,
cobwebby stem. Creamy thistle flowers
from July to September. Flower heads
are 1 1/4 inch high, with creamy white to
pink disk flowers and no ray flowers.
Leaves are up to 8 inches long, bright
green on top and whitish beneath,
extending down the stem, with spines
of varying lengths on the margins. This
thistle is a much lighter pink (or even
white), so it is easy to distinguish from
musk thistle, and is generally taller with
bigger flower heads than canada thistle.
Parry's Thistle
Cirsium parryi
Parry's thistle grows from the foothills
to 10,500 feet tall. Habitat for parry's
thistle is moist meadows and stream
sides. Flowers bloom from mid July to
August. Flowers are greenish -yellow to
yellow. Outer leaves are straight with
terminal spines and spiny margins.
Involucres with long hairs, appearing
cob -webby.
Landowner Name:
Mailing Address:
Appendix C
Pitkin County
Landowner Weed Management Plan
Physical Address of Property:
Phone Number:
Noxious weed(s) to be treated:
Parcel I.D. #
I will be using mechanical control methods (check where appropriate)
mowing hand cutting pulling grazing
I will be using herbicides:
Herbicide (s):
Date(s) of Treatment:
I plan to purchase the services of a commercial weed control company:
Company Name:
Date(s) of Treatment:
Landowner Signature: Date:
Approval: Date:
(Land Manager Signature)
Appendix D
Resource Directory
GOVERNMENT RESOURCES
Agency
Physical Address
Mailing Address
Phone
Website
City of Aspen Parks
585 Cemetery Ln,
(970)
Aspen, CO 81611
SAME
920-5120
aspenpitkin.com
Town of Snowmass
130 Kearns Rd
P.O. Box 5010
(970)
Village
Snowmass Village
Snowmass Village
923-5110
Public Works
CO, 81615
CO, 81615
x 303
tosv.com
Town of Basalt
200 Fiou Lane
(970)
Public Works
Basalt, CO 81621
SAME
927-4723
basalt.net
Pitkin County
76 Service Center Rd.
(970)
Land Mgmt
Aspen, CO 81611
SAME
920-5214
aspenpitkin.com
Office A-103
Eagle County
3289 Cooley Mesa Rd.
P.O. Box 250
(970)
Weed & Pest
Gypsum, CO 81637
Eagle, CO 81631
328-3544
eagle-county.com
Garfield County
0567 County Rd. 352
P.O. Box 426
(970)
Vegetation Mgmt
Rifle, CO 81650
Rifle, CO 81650
625-8601
garfield-county.com
Mount Sopris
258 Center Drive
(970)
Conservation
Glenwood Springs
845-5494
District
CO, 81602
SAME
x 105
Natural Resources
258 Center Drive
(970)
Conservation
Glenwood Springs
945-5494
Service
CO, 81602
SAME
x 106
CO Dept. of Ag.
700 Kipling St.
State Weed
Suite 4000
(303)
Coordinator
Lakewood, CO 80215
SAME
239-4173
colorado.gov
CO Dept of Ag.
750 37.8 Rd.
(970)
Insectary
Palisade, CO 81526
SAME
464-7916
colorado.gov
CO Dept of
15285 S. Golden Rd.
Transportation
Building 45
(303)
Weed Coordinator
Golden, CO 80401
SAME
512-5506
dot.state.co.us
CSU Extension
Campus Delivery 4040
(970)
Fort Collins, CO 80523
SAME
491-6281
ext.colostate.edu
Sopris Ranger District
(970)
620 Main Street
963-2266
White River
Carbondale, CO 81623
National Forest
OR
SAME
OR
Aspen Ranger District
806 W. Hallam
(970)
Aspen, CO 81611
925-3445
fs.fed.us/r2/whiteriver
BLM
2300 River Frontage Rd
(970)
Rangeland Mgmt
Silt, CO 81652
SAME
876-9070
blm.gov
ON THE WEB
Agency
Website
Pitkin County Land Management
www.aspenpitkin.com/weeds
Colorado Weed Management Assoc.
www.cwma.org
Colorado Department of Agriculture
Noxious Weed Management Program
www.colorado.gov/cs/Satellite/Agriculture-
Main/CDAG/1167928159176
Colorado Department of Agriculture
Early Detection and Rapid Response
www.colorado.gov/cs/Satellite/Agriculture-
Main/CDAG/1204322434735
CSU Extension Fact Sheets
www.ext.colostate.edu/pubs/pubs.html#ag
Western Society of Weed Science
www.wsweedscience.org
USDA Plants Database
plants.usda.gov
USDA APHIS Invasive Plant Page
www.aphis.usda.gov/ppq/weeds/weedhome.html
USDA National Invasive Species
Information Center
www.invasivespeciesinfo.gov/toolkit/detection.shtml
North American Weed Mgmt. Assoc.
www.nawma.org
National Invasive Species Council
www.invasivespecies.gov
Federal Interagency Committee for the
Mgmt of Noxious & Exotic Weeds
www.fs.fed.us/ficmnew/index.shtml
EPA Pesticide Safety Programs
www.epa.gov/pesticides/safety
The Nature Conservancy's
Global Invasive Species Team
http://tncinvasives.ucdavis.edu/