corn thistle, cursed thistle, creeping thistle, small-flowered thistle, perennial thistle, green thistle, known in Canada as "thistle"
Canada thistle is a creeping perennial that always colonizes in patches. Plants can reach 1-3 feet high. Canada thistle has an extremely well developed creeping root system that can grow several feet deep.
Leaves are smooth on the surface and deeply lobed with spines on the margins. Flowers are produced in 3/4" diameter purple clusters at the end of the stems in June, July and August.
Canada thistle is often associated with lower maintenance sites such as pastures, fields and road-sides.