Noxious Weed Information

Knotweed plant.

Colorado is seeing a dramatic increase in noxious weeds. These invasive non-native plants have been introduced by accident or as ornamental plants and are devastating thousands of acres of wildlife habitat and natural areas. Left uncontrolled, noxious weeds will form dense monocultures and displace native and desirable plants. Native plant loss affects wildlife that depends on the native vegetation for survival.

Jefferson County’s Invasive Species Management Department works to educate landowners about the affects of noxious weeds and how to manage these unwelcome plants.

Noxious Weed Law

The Colorado Noxious Weed Law and Regulations requires public and private landowners to manage noxious weeds on their property. Under the law, a prioritized list has been established, demanding a higher level of control for some weeds, including eradication and containment.

If a weed is on List A, it has a limited presence in the state and is required to be eliminated.  If it is List B, it may be limited or more widespread.  List B weeds with limited distribution may be required to be eliminated.  The state determines containment areas for List B weeds.  Where the weeds are uncommon the level of control will be eradication. Where the weeds are more common the level of control will be achieved by longer-term management.  These areas are periodically redrawn and can be found at the Colorado Department of Agriculture’s site.


Eradication means the complete elimination of a noxious weed. Eradication occurs when weeds are prevented from forming seeds or developing plant parts that can reproduce.


Containment means controlling noxious weeds and preventing them from spreading to areas where they are not known to grow.


Suppression means managing a specific noxious weed by reducing its population and preventing it from spreading onto neighboring properties.