Canada Thistle

Canada thistle is abundant in Calumet County, where many old fields have been taken over by this noxious weed. It is a 2 to 5 foot dioecious perennial forb with slender, grooved stems that branch only at the top. Stems become increasingly hairy as the plant matures. The leaves are smooth, oblong, tapering, and characterized by crinkled edges with numerous spines along the margins. It has numerous ¾ inch fragrant purple flowers from July to September. Canada thistle thrives in disturbed areas and in a wide variety of soils. It is abundant along roadsides and its seeds are frequently spread by mowing after flowering has begun. Canada thistle is considered a noxious weed under Wisconsin law and should not be allowed to go to seed. For additional information, visit http://dnr.wi.gov/invasives/fact/canada_thistle.htm