Psstthese are the worst invasive plants you should never grow. “We discovered Canada thistle growing in our yard. Should we ...

Non-native species can be particularly invasive, and in particular, Canada thistle poses a major threat to your garden. So unless you are an expert, the best course of action is to remove them.

Canada thistle is a colony-forming perennial from deep and extensive horizontal roots. Stems are 1 to 4 feet tall, ridged, branching above. Leaves are alternate, lacking petioles, oblong or ...

Canada thistle, a terrestrial herbaceous perennial in the Asteraceae family, is an open-land invasive that prefers disturbed upland areas as well as wet areas with water fluctuations. Canada thistle ...

Maps were made from data provided to the Wyoming CAPS Office by Wyoming Weed and Pest supervisors, USDA-APHIS-PPQ, and the University of Wyoming.

European marsh thistle is distinguished from Canada thistle by having spines that cover the stem, leaves, and flowers. For more information visit Midwest Invasive Species Information Network (MISIN).