The problem with learning to identify noxious weeds is that you will then see them everywhere: in your yard, in your neighbors’ yards, along the road, along the trails. They grow everywhere. But the good news is that you can use that knowledge to help identify and eradicate noxious weeds in your area.

Colorado maintains three lists of noxious weeds. These are plants that are nonnative and aggressively out-compete desirable vegetation. The state seeks to eradicate 25 plant species on List A, contain 38 species on List B and suppress 16 species on List C. Find that list at colorado.gov/pacific/agconservation/noxious-weed-species.

The Routt County Weed Program has identified 15 plants from these lists that adversely impact our local environment. Most of these weeds can be contained or eradicated if pulled in the seedling stage, before roots are set. If left to grow, they create a monoculture over time, crowding out flowers and grasses in yards, reducing forage for wildlife and damaging crops.  

Of the 15 weeds identified by Routt County, those from List A include cypress and myrtle spurge, meadow knapweed, orange hawkweed and purple loosestrife. Those from List B include leafy spurge, spotted and Russian and diffuse knapweed, yellow and Dalmatian toadflax, houndstongue and whitetop. This year common mullein (a List C plant) and curly dock were added.

I have not seen any of the List A plants in Routt County yards. On the other hand, I’ve seen many instances of the identified List B plants, particularly whitetop (hoary cress) and houndstongue, along with common mullein and curly dock. Photos of these weeds and management details may be found at co.routt.co.us/DocumentCenter/View/9712/15-Noxious-Weeds-of-Routt-County. I encourage everyone to study this document.

Small stands of weeds like houndstongue or curly dock can be mechanically controlled with a shovel, digging up 4 inches of the taproot, then bagging and disposing of the entire plant. Common mullein can be dug up and seeds carefully disposed of. Identified List A plants and whitetop will likely need chemical control. Chemical control may also be necessary for other List B plants, including Canada thistle and toadflax. Finally, weeded areas should be monitored over the next several years and weed seedlings pulled as they appear.

Photos and the various methods of control for each plant may be found in the links above, or contact Tiffany Carlson, Routt County Weed Program at 970-870-5246 or tcarlson@co.routt.co.us, or Colorado State University Extension at 970-879-0825 and ask for Routt County Master Gardeners or Todd Hagenbuch, agricultural extension agent.

Vicky Barney gardens for wildlife and is a member of the Master Gardener Class of 2011.