(Cirsium arvense L.)
Sunflower family- Asteraceae
Produced by Wyoming Weed & Pest Council in cooperation with Sandoz Crop Protection Corp.
Growth Habit: Perennial, erect, up to 4ft. tall.
Leaves: Varies from light to dark green, oblong or lance shaped, deeply cut, spiny toothed margins (some may be smooth) slightly hairy below. Tremendous leaf variablity.
Stem: Smooth to slightly hairy, branched at the top.
Flower: Small bristly clusters, 3/8 to 5/8 inch in diameter, light lavender to deep rose purple. Plants are male or female.
Roots: Extensive, fleshy, creeping rootstocks.
Seeds: Smooth, light to dark brown, tipped by a cupped conical point, approx. 1/8" long.
Reproduction: by seed and creeping rootstocks.
Habitat: cultivated fields, pastures, rangelands, forests, along roadsides, ditches & riverbanks.
Biological Controls: Canada Thistle stem weevil (Ceutohynchus litura), Thistle stem gall fly (Urophora cardui), Thistle head weevil (Rhinocyllus conicus).
& 24D, Curtail, Escort, Milestone