Yellow starthistle (Centaurea solstitialis)

Yellow starthistle

Centaurea solstitialis


  • Solitary yellow flower at the end of a stem about 1 metre tall.
  • Sharp spines extend out from below the flower head.
  • Stem is erect and blue-green coloured with fuzzy hairs. Grows in bunches and appears bush-like.

Consequences of invasion

  • Infests rangeland and is fatally toxic to horses. The toxin damages nerve centers in the brains of horses, which control eating and drinking habits.
  • Outcompetes native plants and grasses resulting in decreased biodiversity

How is it introduced? How does it spread?

  • This plant is classified as “Prevent” on the provincial Priority Invasive Species in B.C. list, meaning that it is either new or not yet present in BC.
  • Often spread on equipment and vehicles, especially with the transportation of livestock.
  • Seeds have been found in wildflower seed mixes and grass seed.

Management Options

  • It is important to check what seeds are in wildflower seed mixes before they are planted to avoid unintentional planting.
  • Become PlantWise and learn about Grow Me Instead.
  • Livestock that has been in pasture with these plants must not be transported to areas not yet infested.
  • Check all clothing and brush off your boots when leaving an infested area.
  • Small infestations can be controlled by hand pulling before plants flower.
  • Mowing when the plant is beginning to flower is another option.
  • Infestations must be treated as early as possible to be the most effective.

More information available:

US Department of Agriculture: Yellow Star-thistle
Canada Food Inspection Agency: Yellow Starthistle
Alberta Invasive Species Council: Yellow Starthistle