Centaurea jacea is a perennial plant that grows 1-4 ft. (0.3-1.2 m) tall. The stems are ridged and may have purple stripes.
Foliage
The basal leaves are oblanceolate to elliptic and 2-10 in. (5 -25 cm) long. Leaves become smaller as they ascend the stem. These smaller leaves are lanceolate and attach directly to the stem.
Flowers
The brown bracts of the inflorescence give this plant its common name. Flowering occurs from June to October, when rose to purple flowers appear in 1-1.25 in. (2.5-3.2 cm) wide, solitary heads at the tips of the branches.
Fruit
Centaurea jacea produces small light brown, plumeless seeds; about 12 per head.
Ecological Threat
Centaurea jacea is an aggressive invader preferring moister, cooler conditions than other knapweed species. It can tolerate partial shade. It can invade grasslands, open woods, meadows, pastures, woodland clearings, and cutover areas of forest crowding out native plants or forage. Centaurea jacea is native to Europe.