Description:
Black knapweed has broadly lance-shaped basal leaves on a stalk. The leaves are toothed or shallowly lobed to entire. The stem leaves become smaller up the stem and are stalkless. The flowers are rose to lavender and bloom from July to October. Black knapweed is perennial from a woody root crown. The stems are erect, few, and branch near the middle or above and are eight to 32 inches tall. The bases of the stems are sometimes prostrate and rooting at several nodes. The seeds are about 1/8 inch long, ivory-white with lengthwise stripes; ring of hairs or plume pale colored, about 1/16 inch long. The broad comb-like bracts are roundish with dark brown or black fringed margins. The fringe length is up to three times as long as the width of the central part of the bract.

• Mechanical: Fire, tilling and seeding, mowing (clipping), fertilization, improved grazing systems, and combinations of those technologies can control black knapweed.
• Biological: Predator insects and/or parasites.
• Herbicide: Glyphosate, 2,4-D, dicamba, or picloram are adequate, each with its own range of herbicidal effectiveness, relative to season of use and the developmental stage of the plant. Please refer to the recent Pacific Northwest Weed Control Handbook for more information. Read and follow current herbicide labels and recommendations for control. Refer to the State Noxious Weed Control Board site

For More Information:
Detailed information about Black Knapweed is available at the Washington State Noxious Weed Control Board Web Site.