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Home > Weeds > Canada Thistle

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.

Canada thistle Canada thistle leaves Canada thistle flower
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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[Photos, left to right: Jan Samanek, State Phytosanitary Administration,; Jan Samanek, State Phytosanitary Administration,; John M. Randall, The Nature Conservancy,]

It is the policy of the State of Maine to minimize reliance on pesticides. The Maine Department of Agriculture and the Maine IPM Council encourage everyone to practice integrated pest management and to use pesticides only as a last resort. The mention of pesticides in the fact sheets linked to these pages does not imply an endorsement of any product. Be sure that any product used is currently registered and follow all label directions.