Yellow starthistle - Centaurea solstitialis

Weed Seed - Yellow Starthistle (Centaurea solstitialis)

Plant pest card - Yellow starthistle

Yellow starthistle is an invasive plant found in pastures and rangelands. Dense populations of this plant result in lowered yield and quality of forages and occasionally crops. It is poisonous to horses. Infestations of yellow starthistle also decrease the diversity of ecosystems in native grasslands.

Where it's found

In Canada, a few yellow starthistle plants were previously found in Alberta, British Columbia, Ontario, and Saskatchewan, but no populations have persisted to date.

Yellow starthistle is native to Eastern Europe through to central Asia. It has been introduced throughout Africa, Europe, and North and South America. It has been found in many US states.

What it looks like

Yellow starthistle is a winter annual, herbaceous plant. The plants are grayish-green with many stiff stems reaching 15-200 cm tall. The flowers are bright yellow and are ringed with long, sharp spines. Seeds are about 2-3 mm long and are tan with white spots. The dead stalks persist and usually remain standing through the winter.

How it spreads

Seeds move over long distances with livestock, vehicles, equipment and contaminated seed, grain and hay. Seeds have bristles that may also stick to clothing.


Yellow starthistle is regulated as a pest in Canada under the Plant Protection Act. It is also listed as a prohibited noxious weed on the Weed Seeds Order, 2005 2016 under the Seeds Act. Importation and domestic movement of regulated plants and their propagative parts is prohibited.

What you can do about it

  • Use clean grain, hay and straw.
  • Use clean, high-quality seed that is certified if possible.
  • Ensure machinery, vehicles and tools are free of soil and plant parts before moving them from one area to another.
  • Contact your local Canadian Food Inspection Agency (CFIA) office if you suspect you have found this invasive plant. The CFIA will follow up and determine if further action is needed.

Learn more about invasive species.

Yellow starthistle flower
Yellow starthistle flower
Peggy Greb, United States Department of Agriculture–Agricultural Research Service
Yellow starthistle infestation
Yellow starthistle infestation
Steve Dewey, Utah State University (
Yellow starthistle winged leaves
Yellow starthistle winged leaves
Russ Kleinman