Noxious Weed Management in Colorado

Key takeaways from the Colorado Noxious Weed Act

The Noxious Weed Act and associated Administrative Rule are the legal documents that govern how noxious weed management works in Colorado. Some key takeaways are:

Landowners are responsible for management. All public and private landowners in Colorado have a legal duty to control noxious weeds on their property to prevent them from causing damage to neighboring lands.
Counties and municipalities have authority. Local governments are empowered to create and enforce their own noxious weed management plans. These local plans can be more restrictive than state law, allowing them to address unique local weed problems and enforce compliance.
Weeds are categorized by required management. The Colorado Department of Agriculture classifies noxious weeds into different lists (A, B, and C) based on their distribution and the required control efforts, ranging from mandatory eradication for rare species to recommended suppression for widespread ones.

View the Noxious Weed Act View the Administrative Rule

For an alphabetical list of county contacts, click here

Noxious Weed Management Strategies

List B County Management plans can be found here. (To see a county's data, click on its individual tab at the bottom of the spreadsheet.)

List B Rotation Schedule

Here are the key terms used to describe different management strategies:

Eradication means completely eliminating a noxious weed species in a specific area by preventing it from reproducing until its seed bank is gone.
Elimination is the first step of eradication, where all existing plants of a specified noxious weed are destroyed. This is followed by continued efforts to remove new growth until the seed bank is depleted.
Containment involves creating a managed buffer zone to prevent a noxious weed from spreading from infested areas (where suppression is used) into uninfested areas (where eradication is the goal).
Suppression means using various management techniques to reduce the growth, spread, and negative effects of noxious weeds in an infested area.

Designated Noxious Weeds Listing

The Colorado Noxious Weed Act classifies invasive, non-native plants into three main lists (A, B, and C) based on their distribution in the state and the mandatory management requirements for landowners and local governments. This tiered system helps prioritize control efforts to protect the environment and agriculture.

List A: Mandatory Eradication (Highest Priority).

Distribution: Newly arrived, uncommon, or limited populations.
Management Goal: Complete elimination (eradication) from all lands statewide to prevent them from becoming established.
Landowner Requirement: Mandatory Eradication on all public and private lands. It is a violation to allow these species to produce seed or reproduce.
State Role: Implement plans for immediate, statewide eradication

List B: Management, which includes eradication, containment, or suppression, is mandated but varies by county.

Distribution: Discrete statewide distributions; well-established in some areas, but limited in others.
Management Goal: Stop the continued spread into un-infested areas.
Landowner Requirement: Mandatory Eradication on all public and private lands. It is a violation to allow these species to produce seed or reproduce.
State Role: The State Noxious Weed Program develops and oversees customized, county-level management plans—including Eradication, Suppression, or Containment—designed to stop the spread of List B weeds. The state updates its analysis of the entire List B every two years.

List C: Recommended Control (Local Priority)

Distribution: Widespread and well-established throughout the state.
Management Goal: To support local efforts; the state goal is not to stop continued spread.
Landowner Requirement: Control is recommended by the state, but not required by state law. Local governments (counties/municipalities) have the authority to decide if they will require management.
State Role: Provide education, research, and biological control resources to local jurisdictions that choose to require management.

What's the Difference?

Federal Noxious Weed List

The federal noxious weed list, managed by the USDA, includes non-native species that threaten the U.S. It focuses on preventing new introductions by controlling the transport of these plants across state and international borders.

State Noxious Weed List

Each state maintains a noxious weed list tailored to its specific ecological and agricultural needs. These lists, often broader than the federal one, require landowners to control certain weeds and categorize them by management strategies ike eradication or suppression.

Local Noxious Weed List

Local noxious weed lists are created by counties and cities to address specific weed problems in their area. These lists are the most restrictive and local governments are responsible for enforcing weed management on all public and private land within their jurisdiction.