Spotted knapweed (Centaurea maculosa Lam.) is member of the Aster family, Thistle tribe. Native to central Europe, it is a simple perennial that reproduces from seed and forms a new shoot each year from a taproot. The plant can have one or more shoots up to 4 feet tall.
Rosette leaves can be six inches long and deeply lobed. 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 through the summer into fall.
Spotted knapweed occupies dry meadows, pasture land, stony hills, roadsides and the sandy gravelly flood plains of streams and rivers, where soils are light-textured, well-drained, and receive summer precipitation. Spotted knapweed tolerates dry conditions, similar to diffuse knapweed, but will survive in high moisture areas as well.