Cirque Meadows by Adam Johnson
> Departments > Natural Resources > Weed District

Larimer County Weed District

Identify this Weed

Identify This Weed – send us your photo of a weed to identify.

After the Fire

Soil Erosion Control

Vegetative Recovery

The Larimer County weed management program will strive to minimize the occurrence of weeds and associated negative impacts on native plant communities, agricultural lands and public corridors in Larimer County. In doing so, staff will strive to establish and maintain relationships within the community based on best land stewardship practices. We will achieve this through collaborative research and discourse, making ourselves and our resources accessible to the public and continuing education amongst the general public as well as land stewardship professionals.


  • Assist landowners with noxious weed problems through plant identification, weed management recommendations, and development of vegetation management plans.
  • Promote noxious weed education and awareness by way of community presentations, site visits, and tours of collaborative field research plots demonstrating best management practices.
  • Manage noxious weeds on county property and roadside rights-of-way.
  • Enforce the Colorado Noxious Weed Act on non-compliant property owners.

What Are Noxious Weeds?

A weed is often defined as 'a plant out of place'. This simple definition can refer to many different plants in many settings. A 'noxious weed' has a special definition with a legal connotation. The Larimer County Weed District follows the guidelines of the Colorado State Noxious Weed Act which defines 'noxious' weeds as plants that are exotic and invasive. Exotic means non-native, or weed species that originated in other parts of the world. Most of the weed species considered noxious in Colorado originated in regions of Europe and Asia with a climate similar to the Rocky Mountain Region. Invasive plants are those vigorous enough and competitive enough to crowd out desirable plants, and in doing so, decrease native plant diversity and wildlife habitat. The increased vigor and competitive ability of a non-native plant is the result of being introduced into a country with different grazing animals, predatory insects, disease and other limiting factors that kept the species in check in its native land.

The Colorado State Noxious Weed Act lists 71 weed species considered to be a threat to the economy and environment of Colorado. Another 24 species are listed on the state's Watch List. The lists are categorized by priorities:

  • List A species are of the highest priority. These weeds are not well established in Colorado, are potentially a large problem to this state, and require mandatory eradication by local governing agencies. There are seven List A species in Larimer County.
  • List B species are common enough in parts of the state that eradication is not feasible, though the species are still recommended for eradication, suppression, or containment depending on distribution and densities around the state. The County has 16 of these species on the Larimer County Weed List.
  • List C species are widespread and well established.
  • Watch List are species which are on this list to educate and encourage identification and reporting. They are determined by:
    1. Not known to occur in the state but their noxious characteristics are found in the region.
    2. They have been found to display noxious characteristics in plant communities similar to those in Colorado.
    3. They have noxious characteristics as determined by the plant assessment process used by the state, yet their distribution and effect on lands in the state is still unknown.

The Larimer County Noxious Weed Management Plan requires eradication of all List A species, as mandated by the state, and containment and suppression measures for 16 of the List B species identified as significantly troublesome in Larimer County. County outreach programs emphasize identification and management of the 16 List B species but the Weed District reserves the right to enforce on any state-listed noxious weed if infestation size and density deems it necessary. Other species, too common to require control, are still considered troublesome weeds in the County and the Weed District will provide best management practices. The Weed District has also compiled a list of native and non-native plants that are often a concern with Larimer County residents that can be found in Frequently Asked About Pasture Plants. For a comprehensive listing of weeds and to see a summary of the weed law go to Weed Law Summary and Weed Lists.

Contact Information

General Inquiries
(970) 498-5768
Send email

Land Stewardship Manager
Casey Cisneros
(970) 498-5769
Send email

Physical Address
2649 E. Mulberry St, Suite 6
Fort Collins, CO 80524

Office Hours
8 a.m. - 4:00 p.m.
Monday - Friday
Please call ahead for an appointment
(except holidays)

Background Image: Cirque Meadows by Adam Johnson. All rights reserved.