Noxious Weeds & Invasive Species

Noxious Weeds & Invasive Species Management on Open Space


The weed management program is responsible for weed control on:

  • 25,000 acres of land designated as natural areas
  • 7,000 acres of agricultural leased land that serves as wildlife habitat
  • 685 miles of county maintained road right-of-way

The Boulder 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 List B species identified as significantly troublesome in Boulder County. Of the 18 List A species, 10 are currently known to exist in Colorado, and nine of those are known to exist in Boulder County.

Staff utilizes an integrated pest management approach to controlling weeds that include mowing, hand pulling, insect bio-control, cultural control (tilling weeds and planting desirable vegetation), and herbicide application. Herbicides are only used in targeted areas.

When controlling noxious weeds on open space properties, staff are careful to use the least damaging and most effective weed control strategies available. Staff always consider the local ecology to maintain and support the rich ecosystems of open space lands.

Planned Herbicide Applications

Herbicides that may be used, weather permitting, are Endurance, Escort XP, Esplanade 200 SC, Glyphosate Pro 4, Hardball, Milestone, Overdrive, Plateau, Quinstar 4L, Rodeo, Telar XP, Transline, and Tordon 22k. If you have questions concerning herbicides being used, please contact the National Pesticide Information Center at 1-800-858-7378.

Property Listings

  • Ron Stewart Preserve at Rabbit Mountain
  • Please note that properties closed to the public are not listed

Roads & Right-of-Ways

  • All county roads east of Highway 36 have the potential for herbicide application.

Please call the weeds hotline at 303-441-3940 for daily updates.


  • Minimize the occurrence of weeds and associated negative impacts on native plant communities, agricultural lands, and public corridors.
  • Utilize an integrated weed management approach in order to prevent the introduction of new invasive plant species, eradicate isolated or limited populations, and contain and manage weed species that are well established within the county.
  • Stay current with weed management research and innovative management techniques that may increase effectiveness of weed control and/or decrease environmental impacts.
  • Promote education and awareness of new and potential invasive weed species.

What You Can Do

  • Identification and do not plant them in your garden. If they already grow in your garden, remove them.
  • Report a Concern on private property.
  • Parks, Environment, Gardening & Agriculture Volunteer Opportunities
  • Educate friends and neighbors who have these plants growing on their properties. Their plants will likely spread to your property.
  • Minimize spread of weeds on open space by staying on the trails, feeding horses weed free hay, and cleaning weed seeds from your hiking boots or bicycle tires before recreating on open space property.
  • Attend a Weed Identification and Management Workshop through CSU Extension.

Links to Other Websites


Contact Us

Parks & Open Space