(reprint from Sept/Oct 2000 Sego Lily Vol. 23 no. 5)
Wacky Weed Warriors on the Warpath

By Susan Garvin
Utah Native Plant Society

Some of you may be familiar with a non-native annual plant called yellow starthistle (Centaurea solstitialis). It has been declared a noxious weed in 9 western states, including Utah, and two western Canadian provinces. This plant has caused millions of dollars of economic damage to pastures and rangelands in California, Oregon, Washington, and Idaho and is invading other western states rapidly. This weed is known to increase in Idaho at the rate of 60% per year. It has been present in California since the gold rush days, where it was accidentally introduced as a contaminant in alfalfa seed. Currently it is estimated that it has invaded 15-22 % of California's total acreage. It can grow anywhere cheatgrass (Bromus tectorum) can grow and appears to be more competitive in many places.

Centaurea solstitialis I was first introduced to this plant late last summer on a weed tour in eastern Washington and western Idaho. I happened to be wearing sandals, and the tour leader tumbled us out of the bus and strode toward a pasture with no warning of what we were headed for. So all of a sudden I was knee deep in the horrible prickly stuff. It left a lasting impression on me!

Less than a month after my return to Utah, Dea Nelson called to say that Yellow starthistle (YST) had been spotted at the base of Battle Creek Canyon, just above Pleasant Grove. I was horrified and hurried over to have a look. Amateur botanist that I am, I couldn't find it and soon became distracted with other concerns. But Phil Allen, knowing of my detestation for the weed, brought up the nasty subject again in July of this year while I was talking to him by cell phone. He said, "I happen to be standing in a patch of YST, right next to Kiwanis Park."

I couldn't ignore it any longer. I got on the phone to Dea, who got on the phone to Craig Searle, our Utah County Weed Coordinator. He said he knew of it in at least ten patches between Grove Creek and Battle Creek. Knowing how busy Craig is, we decided it was our responsibility as supporters of Utah's native plants to help eradicate this pest from the county before it gets a chance to march up into Uinta National Forest in the very area where bighorn sheep were introduced this spring.

Centaurea solstitialis young plant We also found out that it has been present in Utah County for at least 10 years, in Highland along the American Fork Creek between two golf courses, on the edges of some very expensive recently developed subdivisions and in an alfalfa field. It appears to be contained there and not presently invading surrounding neighborhoods.

We think our only course of action is to go after this weed and eliminate it from our county while it is present only in small numbers. This has been a successful approach in Montana, where the herbarium listings for this plant almost always end with the notation: "ERADICATED!". So three of us went on a search and destroy mission August 24 to the mouth of Battle Creek Canyon. We spent about 40 minutes pulling every plant we could find in the infamous Allen patch (named after our fearless NPS president). Craig Searle agreed to burn it for us so it doesn't have to go to the county landfill. Then I called John Hendrix, the volunteer coordinator for the Pleasant Grove Ranger District to ask for his help on pulling this weed in Highland, since seeds were already fully mature. He promptly came up with 40 eager BYU honor students, who went out with us on September 9 and pulled everything we could find on the banks and environs of American Fork Creek. Thank you John, the Forest Service, and BYU. We have enlisted the help of a retired rangeland monitor named Bill Losee and a Botany and Range Science Master's degree student named Jeff Ott to help survey the bench above Pleasant Grove so we know where to send future volunteer crews and where the county weed crews need to spray late next spring. And we have begun to plan for a community education campaign so this horrible pest will be spotted, reported, and eradicated before it can become the bane of hikers, rock climbers, trailriders, mountain bikers, and other nature lovers of our foothills. Hopefully they will never have to experience, as so many in California and other western states have already experienced, what a nasty weed this is. If we are successful, we would like to extend our campaign into neighboring counties so we can eradicate this weed from the whole state of Utah. Of course, we know that even if we find and pull all of the patches this fall (unlikely), we still have a hard fight ahead of us; 5-10% of the seed can seedbank (live in the soil) for up to 10 years, and it's had 2-10 years to spread its seed already. So it's not a short campaign, it's a war!

Centaurea solstitialis flowers THIS WEED HAS THE POTENTIAL TO WIPE OUT MANY OF OUR NATIVE PLANT COMMUNITIES!! I am not exaggerating the competitiveness of this weed. I have seen entire hillsides in the California Coastal Range and western Sierra Nevada foothills where virtually no other species are growing, let alone native species. Huge private acreages that used to support cattle grazing in Idaho have been completely abandoned. Hell's Canyon is a monoculture of this weed in some places. If we want to enjoy our foothills WE MUST ACT NOW! This weed may just be poised, waiting for the right set of weather conditions or a fire on the hills of Pleasant Grove (or Alpine!) or a disease epidemic in bluebunch wheatgrass to give it an opening which will allow a population explosion of yellow star thistle. Once that happens, it may be too late to stop it. Witness the explosion of squarrose knapweed (Centaurea virgata) that started in the Tintic area of Juab county. This weed is suspected to have been brought to our area in sheep fleece. It was first collected there in 1954 but may have been present in low numbers for 25 years or more before it started to spread. Now it dominates huge acreages in Juab county and it has crossed the border into Tooele and Utah counties. How many millions of dollars will it take to control knapweed now that it is successfully established and our native sagebrush communities in the Tintic area are decimated? How many millions of dollars will we have to spend fighting fires on that degraded wildland?

We dare not wait to ask those questions when a noxious weed is first introduced into our county. Yellow starthistle is the enemy of our foothill plant communities. It's got to go!

If you are interested in helping us fight this weed, please call Susan Garvin (801-377-5717) or Dea Nelson (801-423-3358) to join the Weed Warrior's Brigade. We can use help in getting the word out to our foothill communities and in grubbing out the nasty villain before it can drop seed. We especially need people willing to learn the habits and masquerades of this outlaw plant and hike the bench above Pleasant Grove to spy out the villain and help us get it mapped.

For more information on this desperado search the web using 'yellow star thistle' or 'yellow starthistle' or see Steve Dewey's USU extension WeedWeb site at http://www.ext.usu.edu/ag/weeds/index.htm. The pictures in this article come from that site. Thanks for the great website go to Steve and to USU Extension Service.

Copyright 2000 Utah Native Plant Society