Photo Credit: Steve Dewey, Utah State University, retrieved from Bugwood.org (Image Number: 1459278), used under CC BY 3.0 US, modified from the original
Squarrose knapweed is native to southwest Asia and the Middle East. The method of its introduction into North America is unknown. During the 1950s it became a problematic species on rangeland in the western U.S.
Squarrose knapweed is well adapted to drought and to cold temperatures. It can invade rangeland and out-compete forage species causing a negative impact on livestock and wildlife.
This knapweed has very small flowers that are only 3-8 mm wide. The bracts have a distinctive short spine that curves backwards at the tip.
The leaves are deeply lobed, grey-green in colour and have hairs on the surface. They get progressively smaller from the base to the top of the stem. The fruits usually don't have a plume or bristles.
Squarrose knapweed grows up to 150 cm tall.
Learn more about this species:
See Fact Sheets - Alberta Invasive Species Council