WordNet
black knapweed
n. a weedy perennial with tough wiry stems and purple flowers; native to Europe but widely naturalized [syn: lesser knapweed, hardheads, Centaurea nigra]
Usage examples of "black knapweed".
Centaurea nigra, the Black Knapweed, is a perennial, with an unwinged, erect stem, 6 inches to 3 feet high, generally freely branched in the upper part.