Canada thistle is a perennial weed with yellow flowers. It is considered a noxious weed because it crowds out native plants and is considered to be a weed by many farmers, gardeners, and landscapers across Canada.
It can be identified by its flat leaves that are up to 10 centimeters wide. The leaves do not have teeth at the edges and grow from an underground stem that can be up to 1 meter long. The plant also has small white flowers that bloom in mid-to late summer on short stalks near the leaves of the plant.
Canada thistle has a strong, pungent odor when crushed or pulled apart.