Common knapweed

Centaurea nigra, the common knapweed or black knapweed, is a tough perennial herb of the family Asteraceae growing 30 to 100 cm tall, with stiff, grooved, branching stems arising from a woody rootstock. The lower leaves are lance-shaped and sometimes lobed, the upper leaves narrower and stalkless. The flower heads are solitary at the branch tips, made up of reddish-purple tubular florets emerging from a hard, rounded involucre whose bracts are tipped with a dark brown to blackish, comb-like fringe, giving the plant its name. It flowers from early summer into autumn and is highly attractive to bees and butterflies. Native to Europe and naturalised in North America, common knapweed grows in meadows, rough grassland, roadsides, hedge banks and waste ground.