Definition of "knapweed" []

• Any of various thistles of the genus Centaurea, having variously colored flowers grouped in a head with a spiny involucre. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "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."
• "We saw a lot of wild garlic, scabia, buddleia, bird's-foot trefoil and greater knapweed."
• "I slowly realise that they are stationed right across this marsh in almost every spike of last year's marsh thistle and black knapweed."