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Yellowstone County, Montana
Noxious Weed
Weed Information Contact Department

Canada Thistle
(Cirsium arvense L.)

Sunflower family- Asteraceae

Canada Thistle
Photo by Tom Whitson, Roy Reichenbach

Produced by Wyoming Weed & Pest Council in cooperation with Sandoz Crop Protection Corp.

Canada Thistle Stem

Canada Thistle Rosetta

Canada Thistle Leaf

Canada Thistle Bloom

Canada Thistle Mature

Canada Thistle Dormant

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). 

Herbicides:Tordon & 24D, Curtail, Escort, Milestone

Video Supplied By Ravalli County Weed District