Native Range

Asia and Eastern Europe

Appearance

Russian knapweed is a perennial forb, which reproduces both by seed and vegetatively through its extensive lateral root system. Plant stems are light green, ridged, branched, and typically only up to 3 ft (0.9 m) tall. Rosette leaves are up to 4 in (10 cm) long, gray-green, woolly, and lobed. Stem leaves are alternate and become smaller with smooth margins further up the stem. Flower heads are ½ in (1.3 cm) across with 15–35 pink or lavender florets. Bracts are triangular with a green base and papery tips and margins. The cream-colored seeds are topped by tufts of fine hairs that fall off at maturity.

Impact

Russian knapweed competes with other plants for limited resources and produces compounds that can inhibit the growth of some species. It can form dense infestations, displacing native plant species and reducing range, pasture, and crop production. The bitter taste of its seeds contaminate flour produced from Russian knapweed-infested grain crops. Similar to yellow starthistle (Centaurea solstitialis), Russian knapweed is toxic to horses, causing a chronic and potentially fatal neurological disorder known as “chewing disease”.

Reference

Bean, D.W., J. Littlefield, P. Weyl, S. Daly, and T. Collier. 2023. Russian Knapweed (Rhaponticum repens): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW- 2023-1-RUSSIAN KNAPWEED-P. https://bugwoodcloud.org/resource/files/28119.pdf

Resources

• Element Stewardship Abstract - The Nature Conservancy
• Know Your Knapweeds - North Dakota State University
• Federal Noxious Weed Disseminules of the U.S. - USDA-APHIS
• Weed Field Guide - USDA Forest Service

Selected Images

Maps

Invasive Listing Sources

• Alaska Noxious Weeds
• Alberta Weed Control Act
• Arizona Noxious Weeds
• California Invasive Plant Council
• California Noxious Weeds
• Colorado Noxious Weeds
• Hawaii Noxious Weeds
• Idaho Noxious Weeds
• Iowa Noxious Weeds
• Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Kansas Noxious Weeds
• Michigan Noxious Weeds
• Montana Noxious Weeds
• Nevada Noxious Weeds
• New Mexico Noxious Weeds
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• North Dakota Noxious Weeds
• Ohio Noxious Weeds
• Oregon Noxious Weeds
• Pacific Northwest Exotic Pest Plant Council, 1998
• South Carolina Plant Pest List
• Tennessee Exotic Pest Plant Council
• Utah Noxious Weeds - Contain
• Washington Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40
• Wyoming Noxious Weeds

References