Steve Dewey, Utah State University, Bugwood.org

Identification:

Russian knapweed is a long-lived, deep-rooted perennial with growth characteristics similar to Canada thistle. The weed emerges in the spring from roots and grows to 2 to 3 feet tall and is shrublike with spreading branches. Once established, Russian knapweed spreads mainly by underground root stocks as seed production is limited compared with other knapweed species. The leaves are alternate and lobed lower on the plant while upper leaves are entire. Flowering occurs from June to September and flowers vary from light pink to lavender. The stems die back to the soil surface each year. Two key characteristics distinguish Russian knapweed from spotted and diffuse knapweed. First, the flowers have rounded bracts with transparent tips that are quite different in appearance than the dark bracts of spotted and diffuse knapweed. Second, the root of this perennial is dark brown to black, scaly as if the plant had been burned, and can grow to depths of greater than 20 feet. The flowers of Russian knapweed vary from light pink to lavender.

Biological control:

Exploration and evaluation of biocontrol agents for Russian knapweed are in progress. The gall fly Jaapiella ivannikovi was approved for release in 2009 has established and shows promise for the reduction of Russian knapweed. This insect may soon be available for wider distribution.

From Lym and Travnicek, 2015, NDSU Circ. W-1411.

For full description, growth habits, and other control options: Identification and Control of Noxious and Troublesome Weeds in North Dakota