Russian Knapweed

Turestan thistle, creeping knapweed, Russian cornflower 

 Russian Knapweed is a perennial that differs from Diffuse and Spotted knapweeds primarily in that it has a rhizomatous or extensive root system. Russian knapweed can grow up to 3 feet in height and forms dense colonies due to the root system. The roots are distinguishable by their black color, bark-like texture and by the buds that develop on the shoots. The leaves at all stages are gray green in color due to the fine whitish hairs that are all over the leaves. The leaves are alternating. Lower stem leaves are lance-shaped and deeply lobed and the upper leaves are oblong, toothed and become progressively smaller. Russian knapweed is more likely to reproduce by the root systems than by seeds. This plant is bushy unlike Diffuse and Spotted knapweeds and from June to September it will produce pink to purple flowers and when the plant matures more the flowers will turn a cream color. Seeds are ivory white and have hairy tips which fall off the seed as it matures and a single plant may produce up to 1,200 seeds annually. 

Russian knapweeds have Dark brown to black scaly roots and papery bracts below the flower head. 

Russian knapweed commonly grows along roadsides, pastures, croplands, clear-cuts, irrigation ditches, riverbeds and disturbed lands. This plant prefers to have a clay type of soils and a more arid environment. 

There are herbicides and other control methods that commonly control Russian knapweed. Milestone, Tordon, Escort, Telar, 2,4-D, and Dicamba are the most commonly used herbicides. Mechanical control is often ineffective, and can cause further spread by stimulating rhizome growth. For more information on these herbicides and other control methods contact the Weed and Pest office.  

Russian knapweed does not readily establish in healthy natural habitats and it typically invades disturbed areas. Russian knapweed produces its own herbicide, which inhibits the growth of competing plants. Russian Knapweed is poisonous only to horses and can cause a disease called “chewing disease” that causes prehension of chewing muscles along with other strange clinical signs.