Centaurea Solstitialis
Yellow Starthistle  


Provincial Noxious. Winter annual.
Yellow starthistle has winged, heavily branched, rigid stems covered in cottony hairs. The blossoms are bright yellow, single flowerheads with long, sharp, straw-coloured thorns and the upper leaves are small and sharply pointed. Mature plants are 0.6 - 0.9 m tall.

In horses, yellow starthistle causes a neurological disorder called "chewing disease." It establishes easily on disturbed land and forms dense infestations that reduce the available forage for livestock and wildlife. It may have allelopathic effects on some associated native species.

Yellow starthistle can invade rangelands, pastures, roadsides, cropland, and disturbed habitats. It occupies mid- to high-elevation sites in the US Pacific Northwest, where it is best adapted to dry habitats. It is intolerant of shade. It is not yet known to occur in the province. It is spreading on rangelands and roadsides in neighbouring Washington and Idaho.

Plumed seeds are dispersed by wind shortly after maturity. The outer plumeless seeds remain in the seed head until it disintegrates in the autumn or winter.


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