Extension Viewpoints: Noxious Weed of the Month: musk thistle

Photo courtesy Jamie Jones
Musk thistle goes by many names and is one of the most prevalent invaders in Archuleta County.

By Ethan Proud
PREVIEW Columnist

Musk thistle goes by many names, some too colorful to mention in this article, but the most common is “that purple, prickly plant.” It is one of the most prevalent invaders in Archuleta County and can be spotted in every microclimate from Arboles to Chromo, even up to the high country. 

Musk thistle can be found at elevations reaching from 8,000 to 9,000 feet. If you hike much higher than that, you will be rewarded with some of our native thistles that serve as a reminder that not all prickly plants are your enemy. Archuleta County is home to native thistles at every elevation, but it is only in pristine alpine communities that native thistles can be appreciated without needing to identify invaders that occur alongside them.

Being a biennial, musk thistle is not a difficult plant to control. In its first year, it grows as a rosette and doesn’t produce a flower; this is the prime stage to treat it —whether it is with chemicals or a trowel. In its second year, it produces a bloom and dies back. Any plants that have already gone to seed do not need to be sprayed with herbicide or dug up; just remove the seed head and bag or burn it. Musk thistle, however, is opportunistic and can alter its life cycle to be either winter annual, germinating in the fall and overwintering before blooming the next spring, or a true annual, meaning that it completes its life cycle in a single year. It can germinate throughout the season so it requires diligence to prevent it from establishing a foothold. 

While it may not be difficult to control, it is difficult to eradicate if it has been neglected for several growing seasons. Each plant can produce up to 150,000 seeds, which can remain dormant in the soil for decades. Persistence and early detection is the key to control this species. Mechanical, chemical and biological control are recommended. Musk thistle is a fan favorite of pollinators, so be sure to replant native pollinators after controlling thistle to prevent displacing beneficial birds and insects. 

Archuleta County Weed and Pest is your local resource for managing noxious weed populations and controlling other pests.

Upcoming event

Shred It Day: Sept. 23, 4 to 6 p.m. at the downtown TBK Bank parking lot. Suggested donations are $5 per box. 

Donate to the Archuleta County 4-H program

The Archuleta County 4-H program boasts a membership of more than 150 members annually. Often, these programs rely on fundraisers to help offset the costs of the program, such awards, supplies and, most importantly, leadership opportunities. Members can attend various leadership camps and conferences statewide and even nationally. 

To help our program continue to support our members, we appreciate any contribution you make. To pay online, visit https://client.pointandpay.net/web/ArchuletaCo4H/ and select Contributions and Donations.