centaurea_nigra
1. [ noun ] (botany) a weedy perennial with tough wiry stems and purple flowers; native to Europe but widely naturalized
Synonyms: black_knapweed hardheads lesser_knapweed
Related terms: knapweed
Similar spelling:   Centaurea_cyanus
  Centaurea_scabiosa
  Centaurea_moschata
  centre_of_gravity