Legal Issues - About Noxious Weeds

Can you spot the noxious weeds?

The Colorado Weed Management Act (HB 90-1175) requires all property owners to manage "undesirable plants which present a threat to the continued economic and environmental value of the lands of the state." The law identified four plants for state-wide control: Leafy Spurge, Russian Knapweed, Diffuse Knapweed, and Spotted Knapweed. The law also allows individual counties to name other weeds of local concern. Additional stipulations of the Act:

  • Requires control of noxious weeds on private land as well as along public roads, right of ways and easements.
  • Allows county governments to require agencies (or boards) that supervise or control state lands to also control noxious weeds.
  • Provides county governments the authority to require landowners to control or manage noxious weeds on their property. The Act also provides for arbitration procedures and due process in case a landowner takes no action to control his weeds.

Some examples of appropriate methods of control of the plants stated:

  • Knapweeds - Combine use of control and residual herbicides with mowing to reduce seed production.
  • Leafy Spurge - Residual herbicides alone or in combination with sheep or goat grazing, or use beneficial insect releases in combination with grazing.
  • Canada Thistle - Use a combination of mowing and residual herbicides.
  • Musk Thistle - Primary here is preventing seed production as seeds are viable in the soil for several years. Small infestations can simply be grubbed out by hand. Larger infestations will need mowing in combination with contact or residual herbicides.

Several counties have weed control programs to assist private landowners. Help with weed identification and recommendations for control methods is also available from your local Weed Advisory Board (sometimes part of the local soil conservation district), the County Extension Agent and most USDA offices.

PS: The thistles are included in the above list because they are also among the most troublesome weeds found in Colorado and New Mexico. As thistles tend to take over your best soils, they can cause significant damage to any farm or ranch operation. logo
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