Any of several plants with tough stems or roots; esp. (a) knapweed, esp. black knapweed, Centaurea nigra, and greater knapweed, C. scabiosa; (b)…

Any of several kinds of knapweed, spec. hardhead knapweed, Centaurea nigra (also black matfellon) and greater knapweed, Centaurea scabiosa.

Black knapweed, Centaurea nigra. Cf. hardhake, n., hardhead, n.2 5.

the knapweed (Centaurea nigra); = boll-weed n. at boll, n.1 compounds.

a name for Matfelon, or Knap-weed.

The common name of species of Centaurea (family Compositæ), esp. C. nigra, a common weed with a hard tough stem, and light purple flowers set on…

the knapweed, Centaurea nigra.

Any of several knapweeds, typically having hard flower buds; spec. the black knapweed, Centaurea nigra. Frequently in plural with singular agreement.

(a) (North American) any of several herbaceous plants of (or formerly included in) the related genera Spermacoce and Diodia (family Rubiaceae)…

Any of several knapweeds, genus Centaurea, having hard globular flower buds; esp. common or black knapweed, C. nigra.

Any of various plants growing as weeds of cultivated land and typically having tough or wiry stems; spec. (a) black or common knapweed, Centaurea…

Name for various species of Centaurea (Knapweed, etc.), from the knobby ‘heads’.

English regional. The common or black knapweed, Centaurea nigra. Cf. hardhead, n.2 5. Now rare.