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
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.

Canada thistle leaves
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.

Canada thistle flower
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,]