Brown knapweed is an agressive invader, considered to be noxious in many states. The species prefers moister, cooler climates than other knapweed species and can tolerate partial shade. A hybrid of Brown knapweed and Black knapweed is fertile and widespread in the northeastern US.
Brown knapweed is a perennial native to Europe and was introduced to the United States. The herb is found in disturbed habitats, meadows and fields, cleared woodlands, and sometimes in wetlands.
Brown knapweed produces rose to purple flowers from June to October. Each head produces about 12 small, light brown, plumeless seeds.