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. The list is 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 six 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 13 of these species on the Larimer County Weed List.
List C species are widespread and well established.
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 13 of the B species identified as significantly troublesome in Larimer County. County outreach programs emphasize identification and management of the 13 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. There are also several weed species that were once sold by nurseries as ornamentals and have spread out of gardens to become a nuisance. They are known as escaped ornamentals. 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 Weeds. For a comprehensive listing of weeds and to see a summary of the weed law go to Weed Law Summary and Weed Lists.
District Manager
Tim D'Amato
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Physical Address
2649 E. Mulberry St, Suite 6
Fort Collins, CO 80524
Mailing Address
PO Box 1190
Fort Collins, CO 80522
Phone
(970) 498-5768
(970) 498-5776 Fax
Office Hours
8:00 a.m. - 4:30 p.m.
Monday - Friday (except Holidays)
Call ahead during winter