Knapweeds are noxious weeds in Colorado which belong to the Carduoideae clade, also known as thistles and allies.
This grouping of the aster family classifies knapweeds, burdock, artichokes, cornflowers and other plants into a broader category of sharing genetic and phenotypic traits with the thistle family.
When looking at the blooms of spotted or Russian knapweed, it’s easy to confuse them with those of Canada thistle.
Knapweeds, like thistle, lack gray florets, which give other members of the daisy (aster) family their classic and recognizable look. Russian knapweed exhibits an erect growth habit and creeping root system similar to Canada thistle, but has blue-green shoots and lacks the spines.
Spotted and diffuse knapweed have a spherical growth pattern and are biennial to short-lived perennials.
Reference back to the thistle article, and the management options are the same-Canada thistle and Russian knapweed can be managed in the same style, while spotted/diffuse knapweed and musk thistle are analogous in terms of management.
However, all three knapweed species that occur in Archuleta County can be managed with biocontrols.
Russian knapweed is managed by two galling agents, a midge and a stingless wasp. The midges cause the blooms to gall and therefore do not produce seed, and the wasp lays its eggs in the stems and branches, causing stunted growth. Both of these agents have been released across the county and nearly all Russian knapweed populations exhibit symptoms of damage.
Spotted and diffuse knapweed can be managed with a guild of herbivores including seedhead-feeding weevils and root-boring weevils. These agents have been released by private landowners in the county, though the Archuleta County Weed and Pest Department would like to find more suitable release locations.
Russian knapweed is primarily found on the western end of the county with major populations in the Arboles area, while spotted and diffuse knapweed populations are spreading along the U.S. 84 corridor.
When recreating in areas with knapweeds, utilize PlayCleanGo ethics and wipe any mud or plant parts off your shoes and clothes to prevent spreading these species further.
Knapweeds are toxic to horses and when grazed heavily enough they cause “chewing disease,” where the animal no longer has the motor function to graze and it will starve to death. Typically, knapweeds are not selected as forage, so unless a pasture is heavily infested, animals will avoid it.
Other knapweeds that are on the Colorado Noxious Weed list include yellow starthistle, meadow knapweed and squarrose knapweed. Yellow starthistle has been detected in Montezuma, La Plata and Rio Grande counties. Meadow knapweed has been reported in Rio Grande, Ouray and Dolores counties. Squarrose knapweed has not been reported in Colorado yet, but is present in Utah. When you are recreating or working outside, keep an eye out for these potential new invaders.
Archuleta County Weed and Pest is your local resource for managing noxious weed populations and controlling other pests.
Be Prepared for an Emergency workshop
Don’t miss the “Be Prepared for an Emergency” workshop May 9 at 9 a.m. at the CSU Extension building at 344 U.S. 84.
This free workshop will bring together area experts to cover the best practices for preparing for and recovery from an emergency.
Learn to can dandelion jelly
Learn all the latest food safety preservation practices on May 15 at 5:30 p.m. at the CSU Extension office. The cost is $25 per person/date for one jar of jelly. Call (970) 264-5931 to register today.
Bioblitz
Save the date for Archuleta County’s first annual Bioblitz: June 20 from 8 a.m. to 8 p.m.
Join us for a day exploring the natural areas along the San Juan Riverwalk and Reservoir Hill while collecting valuable ecological information.
This is a fantastic opportunity to connect with nature and appreciate the vibrant life that thrives in this ecosystem.
No prior experience is necessary, just bring your curiosity and enthusiasm for nature.
The cost is $25 per adult and $10 per student/child, includes dinner, a T-shirt and a fun day of learning.
To learn more and to register, visit https://secure.rec1.com/CO/pagosa-springs-co/catalog?filter=c2VhcmNoPTQyNjMyMzY= or email Cindi Galabota at cindi.galabota@colostate.edu.
Volunteer for the Archuleta County Fair
Be a part of preserving the rich heritage and timeless tradition of the Archuleta County Fair and help plan the 75th anniversary Fair in 2026.
You’ll contribute to an annual tradition that brings our community together, supports local agriculture and creates lasting memories for generations to come.
To learn more, contact Tonya Steadmon at tsteadmon@archuletacounty.gov or (970) 264-5931.
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