• WordNet 3.6
    • n knapweed any of various plants of the genus Centaurea having purple thistlelike flowers
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Webster's Revised Unabridged Dictionary
    • n Knapweed (Bot) The black centaury (Centaurea nigra); -- so called from the knoblike heads of flowers. Called also bullweed.
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Century Dictionary and Cyclopedia
    • n knapweed 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.
    • n knapweed Specifically, C. nigra, also called buttonweed, hardhead, loggerhead, and by various other names. It is a perennial branching weed, with rose-purple flowers and a globular involucre, whose bracts bear a stiff and fringed, dark-colored appendage. It is native in Europe and Asia, and sparingly introduced in America northward on the Atlantic coast. Also knopweed and knobweed.
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Chambers's Twentieth Century Dictionary
    • n Knapweed a general name for plants of the genus Centaurea of the composite family—star-thistle, bachelor's buttons
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Chambers's Twentieth Century Dictionary
Conn. with knob, knop.


In literature:

The Black Knapweed is a stiff, soldierly plant, not unlike a small Thistle without prickles.
"Flowers Shown to the Children" by C. E. Smith

In news:

Spotted knapweed an issue in Missouri.
Spotted knapweed was reported in Missouri in 1933 and is established in about 40 percent of the state.
Spotted Knapweed flowers are pinkish-purple and visible during July and August.
It's not clear why Michigan beekeepers are so worried about knapweed control when those in other states haven't been as much.
Some in the industry speculated Michigan beekeepers may rely on knapweed more for nectar and pollen than those in other states.
Spotted Knapweed is seen in Montana.
The commonly seen stiff, bushy herbaceous floral/plant with it's one inch in diameter light purple pom pom flowers is spotted knapweed.
Prickly Pear Braggot was made with Knapweed honey from north west Montana and Red Prickly Pear juice from the Southwestern United States.
Diffuse Knapweed, a noxious weed, is already in the Mountain Shadows neighborhood and ready to invade the already devastated area.
Becker County Ag Inspector Marsha Watland demonstrates how she collects the tiny weevils that are used to control the noxious weed known as spotted knapweed.
Spotted knapweed is driving out native plants and destroying rangeland, costing ranchers millions.