Leaves on shoots are smaller and finely divided, becoming smaller toward the top of the shoot, and are covered with fine hair. Flowering heads are solitary and occur on shoot tips. They are up to one inch in diameter. Flower color usually is lavender to purple. Seed head bracts are stiff and black tipped, with five to seven pairs of short, feathery appendages.
Seeds germinate in spring or fall.
Perennial plants resume growth in early spring and bolt at approximately the same time as diffuse knapweed. Flowering occurs throughout the summer into fall. Spotted knapweed occupies dry meadows, pasture land, stony hills, roadsides, and the sandy or gravelly flood plains of streams and rivers, where soils are light textured, welldrained, and receive summer precipitation. Spotted knapweed tolerates dry conditions, similar to diffuse knapweed, but will survive in higher moisture areas as well. This plant is one of four weeds that must be managed statewide in accordance with the Colorado Weed Management Act.