Plumeless Thistle

(Cardius acanthoides)

plumeless thistle flower
Gary L. Piper, Washington State University, Bugwood.org
plumeless thistle plant
Steven Katovich, USDA Forest Service, Bugwood.org

Introduced from Eurasia, this is a winter annual or biennial which reproduces by seed. This plant can be distinguished from musk thistle by its smaller flowers from 1/2 to 1 inch in diameter. The leaves of plumeless thistle lack the prominent white margin present on musk thistle leaves. The plant may grow to a height of 5 feet or more. Flowers are reddish-purple and can be solitary or clustered. Taproots are large and fleshy.

Plumeless thistle is an extremely prolific seed producer. It is found in pastures, river valleys, and along roadsides. It is found throughout southern Garfield County and is becoming a problem south of Battlement Mesa.