Canada Thistle—Cirsium arvense
A creeping perennial, Canada thistle is a major agricultural pest in crops, pastures and rangelands, and can also be found in meadows, lawns, gardens, roadsides, sand dunes, waste areas and streambanks.
An extensive creeping rootstock allows plants to expand up to 12 square feet in area per year. Stems are slender, grooved and erect, up to 4 feet tall, and branch only at the top.
Leaves are lance-shaped, irregularly lobed with prickly margins, 6 to 10 inches long, about 1 inch wide and attach directly to the stem. Young leaves are hairy and dark green.
Flowers are pink, purple, or rarely white. They form rounded, umbrella-shaped clusters at the ends of the top branches. Flowers present June to August.
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Identification and Control Information
- Fact Sheet with Description and Management Options (PDF) —Plant Conservation Alliance's Alien Plant Working Group
- Fact Sheet with Description and Control Options (PDF) —USDA Forest Service
- Canada Thistle—Wisconsin Department of Natural Resources
- Canada Thistle—The Organic Weed Management Website—Cornell University
More Information
- Weeds and Your Garden brochure (PDF) —New York State IPM Program and Cornell Cooperative Extension
- Weed Management in the Home Garden (PDF) —Iowa State University Extension
[Photos, left to right: Jan Samanek, State Phytosanitary Administration, Bugwood.org; Jan Samanek, State Phytosanitary Administration, Bugwood.org; John M. Randall, The Nature Conservancy, Bugwood.org]