“The musk thistle isn't too bad; you can dig up the rosettes or even pull and bag this and then the plant will be dead and gone.””

Jennifer Cook

GILPIN COUNTY – A large group gathered Wednesday evening at Very Nice Brewing Company to learn how to identify and manage noxious weeds in Gilpin County.

The parking lot was completely full, and not a single seat was available in the large brewery room.  

The free talk, hosted by Gilpin CSU Extension, was led by Jennifer Cook, Extension Director and Specialist in natural resources, horticulture, and energy.

“My name is Jennifer, I'm with the Gilpin County CSU Extension Office, and I'm also the County Weed Manager,” Cook said at the start of the talk. 

“I'm here to talk about noxious weeds, and I'm so excited that everyone is here and interested.”

Cook used live plant samples and interactive discussion to walk participants through a variety of weed species, explaining their life cycles and how to manage them effectively.

Controlling noxious weeds is about more than just landscaping. 

These aggressive, non-native species crowd out native plants and degrade the local ecosystem, threatening food sources for moose, deer, pollinators, and other wildlife. 

She said most of the weeds are foreign invaders from Europe and Asia, and could have been introduced as ornamentals. 

Scentless chamomile

This annual weed resembles oxeye daisy, but the leaves are fern-like.

“These are just annuals so they're pretty easy to pull out of the ground and I would bag this because it already has flowers on it.” 

She added, “It's not the same plant as the one that you would make tea out of. That's a different variety of chamomile so don't try to make tea out of this one, it won't taste good.”

Cheatgrass

“This grass is called cheatgrass and it's an annual,” Cook explained. Its fuzzy stems make it identifiable, and it’s easily pulled when young. 

“This was the main grass that kept [the Marshall Fire] just moving along quickly down there,” she said. “If you get it before the seed head has established... pull it and just leave it on the ground.”

Common mullein

Cook displayed both stages of the biennial mullein, also known as “cowboy toilet paper.” 

“So the first year it has these fuzzy leaves against the ground,” she said. “And then the second year it shoots up this stalk and it has a yellow flower on it.” 

Cook confirmed the medicinal value of the plant to treat the lungs, sharing that she makes her own mullein tincture and smudge sticks. 

Leafy spurge

“This one is called leafy spurge and it's called spurge because the seeds explode from the flowers,” Cook said. 

“Be careful because this sap is really toxic, if you get it on your skin it can cause rashes... it can cause blindness.” 

The milky sap is a key identifier. “It's really toxic for livestock as well... but goats can actually graze this.”

Yellow toadflax

Cook described yellow toadflax as another aggressive perennial. 

“It kind of looks like the flower is butter and eggs,” she said. Though similar in appearance to leafy spurge, it lacks the milky sap. 

“If you have a small patch, it would probably be worth your time to dig it up,” she advised. “But once it's a really big area, it's just impossible to manage that way.”

Musk thistle

“This is musk thistle,” Cook said, holding a sample of the biennial species. “The musk thistle isn't too bad; you can dig up the rosettes or even pull and bag this and then the plant will be dead and gone.”

Canada thistle

A common perennial in Gilpin County, Canada thistle is one of the most difficult weeds to manage. 

“Canada thistle however is much more aggressive; you keep pulling this and you just have to be very persistent or spray it,” Cook said. 

She also noted, “You can cut off the roots after you dig it up... they're really good if you chop them up and put them in the skillet with some sesame oil... and throw some soy sauce on when it's finished.”

Both thistles have pink to purple flowers. 

Diffuse knapweed

“This one is called diffuse knapweed,” Cook said. “It's a short-lived perennial and it's just another not-fun weed to have.” Its flower color varies between white and pink and may appear bushy in mature patches.

Oxeye daisy

Oxeye daisy is a perennial with shallow roots, often confused with ornamental Shasta daisies. 

“These are very aggressive and it's a harder one to manage too,” Cook said. “If you want to dig these out it's hard to not get collateral damage with digging out some of the natives as well.”

Before wrapping up, Cook reminded attendees about available resources. “We do have an herbicide checkout program at our office,” she said. 

“If anyone is interested in spraying weeds that you found on your property, you can check out the sprayer and herbicide... for a $125 deposit that you get back when you return everything.”

To learn more or get help identifying plants, residents can visit https://gilpin.extension.colostate.edu or contact Jennifer Cook at jennifer.cook@colostate.edu or 303-582-9106. 

A complete list of noxious weeds in Colorado can be found at https://ag.colorado.gov/conservation/noxious-weeds.