Canada thistle has become very well established in North America and is now considered a noxious weed in at least 35 states and much of Canada.
Canada thistle rosette with spiny tips and shiny
green wavy leaves.
The smooth, light brown to straw colored achenes are 0.1 to 0.2" long with a conical point; are loosely attached to a tannish pappus at the tip.
Male flower of Canada thistle with pollen-producing stamens. Heads are usually less than 1 inch in diameter with short spines.
Female purple flowering Canada thistle ecotype with a green stem.
White flowering form of Canada thistle which occurs in about 10% of the population.
Canada thistle achenes are attached to a pappus which allows long distance movement in the wind or on farm machinery, a major method of movement to new areas.
Canada thistle ecotype with dark lavender stems and flowers.
Bolted Canada thistle with alternate, waxy wavy leaves, and clusters of flower heads.