from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun Any of various weedy thistlelike plants in the composite family having flowers grouped in a head with a spiny involucre, especially several species of the genus Centaurea and the Eurasian species Acroptilon repens.

from The Century Dictionary.

  • noun A general name for plants of the genus Centaurea of the composite family, as C. Calcitrapa, the star-thistle, and C. Cyanus, bachelor's-buttons.
  • noun Specifically, C. nigra, also called buttonweed, hardhead, loggerhead, and by various other names.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Bot.) The black centaury (Centaurea nigra); -- so called from the knoblike heads of flowers. Called also bullweed.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun Any of various common weeds of the genus Centaurea

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun any of various plants of the genus Centaurea having purple thistlelike flowers


from The American Heritage® Dictionary of the English Language, 4th Edition

[Middle English knopwed : knop, knob; see knop + wed, weed; see weed.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

Alteration of knopweed.


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  • We saw a lot of wild garlic, scabia, buddleia, bird's-foot trefoil and greater knapweed.

    Country diary: Longburton, Dorset 2011

  • She had walked the trail years ago, long before Hinkley Point C had reached its earliest draft on the planning board, and she had seen the blue and copper butterflies and the pale flax and the golden birds' foot trefoil and the royal purple proud-headed knapweed.

    Margaret Drabble | Trespassing 2011

  • I slowly realise that they are stationed right across this marsh in almost every spike of last year's marsh thistle and black knapweed.

    Country diary: Claxton, Norfolk 2011

  • Researchers in Michigan released bugs that feed on spotted knapweed earlier this year.

    Will Killing This Invasive Plant Harm Bees? AP 2010

  • Mauve scabious and darker purple knapweed wave their heads in the aftermath of a summer thunderstorm.

    Butterflies: out of the blue 2010

  • A few swallows swoop low and the rank green is broken by pink hemp agrimony, cream meadowsweet, blue tufted vetch and purple knapweed.

    Country diary 2010

  • In an open woodland glade on a bank of old limestone spoil covered in grasses, black knapweed, wild basil, pyramidal orchids and harebells, many butterflies were making the most of the sunshine, and the air was full of their strobing brown, gold and white wings.

    Country diary: Wenlock Edge 2010

  • Michigan officials don't expect to wipe out knapweed; the hope is to pare it back.

    Will Killing This Invasive Plant Harm Bees? AP 2010

  • Somehow their snapping flight filled the space of the clearing and then they landed on dark purple knapweed flowers to feed.

    Country diary: Wenlock Edge 2010

  • Hemp agrimony, bird's-foot trefoil and knapweed attracted the attention of commas, common blues, red admirals and the only painted ladies we've encountered so far this year.

    Country diary: Durham coast 2010


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