Russian knapweed

Identification & Biology
Alias' : Turkestan thistle, creeping knapweed, mountain bluet, Russian cornflower, hardheads, tumbleweed
Latin Name : Acroptilon repens
Category : Terrestrial Plants
Description :
  • Long-lived perennial plant up to 1 m tall 
  • Grows in dense patches of single erect, stiff stems  
  • Deep, creeping roots and stems 30-100 cm tall  
  • Young stems are covered with soft, short, gray hairs  
  • Solitary, greenish-grey urn-shaped flower heads  
  • Urn-shaped purple or pink flowers (become straw colored at maturity) 
  • Leaves are alternate and oblong to lance shaped 
  • Seeds are oval, flattened, grey to ivory in color, and 2-3 mm long 


Russian knapweed produces seeds, but reproduces primarily by sprouting buds from its spreading root system. This sprouting results in dense, cloned patches of plants. Russian knapweed is similar to diffuse and spotted knapweeds, however, Russian knapweed spreads through creeping horizontal roots and seed, unlike diffuse and spotted knapweeds. Russian knapweed shoots emerge early in spring, and forms rosettes and bolts in late May to mid-June. Russian knapweed flowers from July to September. One plant may produce 1,200 seeds per year. Seeds are dispersed in contaminated soil, hay, and other seed.

Russian knapweed is commonly confused with spotted and diffuse knapweeds, but can be distinguished by the pointed papery tips of the floral bracts. Many native members of the Asteraceae family also resemble Russian knapweed in the rosette stage.  

Look Alikes

Native to Mongolia, western Turkestan, Iran, Turkish Armenia, and Asia Minor, Russian knapweed is a highly competitive knapweed variety. Russian knapweed was first introduced to Canada around 1900 as a contaminant of Alfalfa seed. It is currently found in the largest concentrations in the Keremeos area, and in smaller patches in the east Kootenay region, Okanagan, Merritt, Kamloops and William’s Lake areas. Russian Knapweed thrives in any soil, but does very well in clay soil. Russian knapweed prefers open areas and well-drained soils and can become established in grasslands, open forests, and along roadsides and right-of-ways. However, it is intolerant of shade, prolonged drought, and wet sites.  

Impact & Risks
  • Knapweed plants are highly competitive, forming dense colonies in disturbed or overgrazed lands.  
  • Once established, knapweed can dominate an area and significantly reduce desirable vegetation.  
  • Russian knapweed is particularly a threat to the stability of ranching operations. Russian knapweed can reduce available forage and crop values and may even significantly devalue the land itself.  
  • Other losses include soil erosion and reductions in wildlife populations due to the decrease in forage production.  
  • Grazing animals generally avoid knapweed due to its bitter taste; however, under poor-range conditions animals will graze knapweed.  
  • Russian knapweed is toxic to horses and can cause the neurological disorder, chewing disease. This disease is limited to horses and does not occur in cattle, sheep or goats.  
Prevention & Mitigation

The most effective way to ensure that your lands do not become infested with Russian knapweed is by prevention. Here are some recommendations to prevent invasion on your property: 

  • Maintain grasslands in a healthy, vigorous condition to ensure a productive plant community; competitive perennial grasses and forbs utilize water, nutrients and space that would otherwise be readily available to knapweed.  
  • Regularly patrol your property for knapweed plants and immediately treat new infestations before seed set. Do not leave plants to compost as they may still produce viable seed.
  • Cooperate with adjacent landowners and encourage them to control knapweed and other weeds.  
  • Immediately revegetate disturbed, bare soils with a suitable seed mix that provides dense, early colonization to prevent weed invasion.  
  • Clean your vehicles and machinery of plant material and soil before leaving a knapweed infestation.  
  • Check seed for contaminants and use only certified seed.  
  • Learn to identify the different species of knapweed and other noxious weeds.  
  • Do not move contaminated soils to a new area. 
Treatment & Disposal
  • A combination of cutting and herbicides can be used to manage Russian knapweed. 
  • Cutting or mowing will reduce the current year growth and may eliminate seed production, but will not kill Russian knapweed. Plants should be mowed or cut aggressively several times before plants bolt to weaken the root reserves. Wherever possible, the root system should be removed to prevent re-sprouting. 
  • If plants have not yet flowered, the removed plants can be left onsite, but stems should be twisted, bent, or otherwise crimped.  
  • If treatment is performed while flowers are present on stems, the plants must be bagged and removed from the site, and taken to a landfill. 
  • Areas free of Russian knapweed should be monitored annually and all plants found should be destroyed immediately. 
  • Before applying herbicides, read the label for full use and precautionary instructions. For further information on the selection and application of chemicals to protect your crop, contact AgriService BC at 1-888-221-7141 or email
  • A nematode biological control agent, Scubanguina picridis, has been experimented with in B.C. and Colarado but is currently not available for general distribution. Biological control agents that attack diffuse and spotted knapweed will not transfer to Russian knapweed. 
  • Fire is not an effective agent against this plant.
Okanagan Distribution

Priority Level Definitions

Watch For - Poses a significant threat (very high risk) and does NOT presently occur in the region OR is relatively new to the region and is very limited in extent.
High - High risk/impact; limited population with significant potential to spread in the region.
Medium - Medium risk/impact; limited distribution – broader population distribution with potential to spread further in a region.
Low - Low risk/impact; may be widespread or not, may be of concern in specific situations with certain high values – e.g. specific agriculture crops. Some species may be treated primarily with biological control agents.