Please click on the pictures to view them as a larger size. Canada thistle is a 2 to 5 foot dioecious perennial forb with slender, grooved stems that branch only at the top.
Stems are slightly hairy when young and progressively more hairy as the plant matures.
The leaves are smooth, oblong, tapering, somewhat lobed, and characterized by crinkled edges with numerous spines along the margins. The small, light-brown seeds are slightly tapered, and have a tuft of tan hair loosely attached to the tip to enable wind dispersal. Canada thistle is native to Europe, not Canada, as its name suggests. Its current range encompasses the northern portion of the United States east of the Rocky Mountains. Canada thistle is considered a noxious weed under Wisconsin law and should not be allowed to go to seed.