Definition of knapweed in English:



  • A tough-stemmed plant of the daisy family that typically has purple thistlelike flower heads, occurring typically in grassland and on roadsides.

    See also hardheads
    • ‘In Montana, gall flies released to limit knapweed turn out to provide a food bonanza for white-footed mice.’
    • ‘Currently, most producers apply chemicals on rangeland in spring or summer, when knapweed begins to flower, but research is showing that fall application may be preferable.’
    • ‘Spotted knapweed is not killed by fire, but sagebrush is.’
    • ‘The oil from the seeds of cotton thistles was extracted for fuel and knapweed, centaurea scabiosa, was believed to promote healing of bruises and wounds.’
    • ‘Invasive weeds such as cheatgrass and knapweeds have settled on some 125 million acres of the American West.’


Late Middle English (originally as knopweed): from knop (because of its hard rounded involucre or ‘head’) + weed.