[Orig. knopweed, f. KNOP sb.1 + WEED sb.; from the hard rounded involucre.] The common name of species of Centaurea (N. O. Compositæ), esp. C. nigra, a common weed with a hard tough stem, and light purple flowers set on a hard rough dark-colored globular ‘head’ or involucre.
α. 14[?]. MS. Laud 553 lf. 13. Iasia nigra … is an herbe yt me clepitth maidfeloun or bolwes or yrnehard or knopwed.
1530. Palsgr., 236/2. Knoppe wede an herbe.
1691. Ray, Coll. Words, Postscr. 171. For Knapweed, Knopweed, because of the knops at the top.
1787. Withering, Brit. Plants (ed. 2), Knopweed.
1863. Prior, Plant-n., Knap-weed, Knop-, or Knob-weed.
β. 1597. Gerarde, Herbal, II. ccxxxviii. 588. Matfellon or blacke Knapweede is doubtlesse a kinde of Scabious … the flowers do grow at the top of the stalks, being first small scaly knops, like to the knops of Corne flower.
1656. W. Coles, Art of Simpling, 38. Some grow in knaps like bottles as knapweed.
1785. Martyn, Rousseau’s Bot., xxvi. (1794), 401. Common or Black Knapweed … which the country people in some places call Hard-heads.
1896. R. F. Horton, in Sunday Mag., Nov., 722. Within the enclosure were ragwort, knapweed, and scabious.
