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Home>Plant Species>Weed Species>Yellow starthistle

Drawing of yellow starthistle Yellow starthistle
Centaurea solstitialis

question markDid you know?

Yellow starthistle seedheads hitchhike by jabbing spines into passing hide, clothing or tires!

How did Yellow starthistle get here?
Yellow starthistle, actually related to the knapweeds, began its new life in America sometime around 1849. It most likely came from its native Europe in shipments of alfalfa seed. Multiple introductions occurred, with the first of these in California. Road building, development, and expansion in the ranching industry contributed to the rapid and long-range establishment of new satellite populations.

Yellow starthistle flowerheadsWhat are its characteristics?
Fully mature, this winter annual forb stands about 3 feet tall and has yellow flowers and very spiny flower heads.  As many as 10,000 seeds can be produced by each plant. These hitchhike by jabbing sharp spines into passing hide, clothing or tires. Once in the soil, these seeds can lie dormant for more than 10 years until conditions are right to sprout. A rosette forms in the fall or early spring and then a flowering stalk bolts in early summer.  Dense stands develop that are nearly impossible to walk through because of their menacing spiked flower heads.

Why is Yellow starthistle a problem in the Great Basin?
Yellow starthistle invasion has been likened to the dreaded leafy spurge. It has an advantage over native plants because it matures earlier in the season.  Its roots rapidly grow as far as 3 feet down into the soil stealing water and nutrients that the native plants need to survive the hot summer. Yellow starthistle degrades wildlife habitat and chokes out desirable species with ruthless indifference. ‘Chewing disease’ results when horses eat yellow starthistle. This disease affects their nervous system and is usually fatal.

Yellow starthistle plantsHow can we fight this weed?
You can help prevent the spread of yellow starthistle by inspecting your vehicle or clothing after you have traversed an infested area. Using certified weed free horse feed is a must to prevent its establishment in pastures. Six biological control insects attack the seedhead of yellow starthistle, effectively limiting the number of seeds the plants are able to produce. Sheep, goats, and cattle can graze on yellow starthistle in early spring before the spines develop, and may reduce seed production. Prescribed burning can kill yellow starthistle, but requires careful timing and may affect biological control insects. Application of herbicide during the winter is safer for associated desirable plants and kills fall rosettes of yellow starthistle. Refer to the Weed Management Handbook on the University of Wyoming Extension website for up-to-date herbicide information.

-Drawing: USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 3: 560.
-Flower: Intermountain Herbarium.
-Infestation: J.S. Peterson @ USDA-NRCS PLANTS Database.

Text references:
-USDA, NRCS. 2006. The PLANTS Database (, 26 September 2006). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
-Whitson, T. D., 2000. Weeds of the West., 9th ed. Western Society of Weed Science, Newark, CA.
-Zouhar, Kris 2002. Centaurea solstitialis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: (, 26 September 2006).