Russian Knapweed
Scientific Name: Centaurea repens

History/Origin
          Like other knapweeds, Russian knapweed is native to Eurasia (central Europe and East to central Russia) and was introduced into America around 1898. It is now considered a noxious weed in 21 Western states.

Biology/Ecology
          A single Russian knapweed plant can produce over 1,200 seeds, each remaining viable for 2-3 years. Seeds are known to be dispersed by some mammals, recreationists, crop harvest, transportation of infested topsoils, and contaminated vehicles. Seed dispersal allows this plant to spread into new areas, but once established, most reproduction within a site comes from adventitious buds on their black roots. Roots can grow 6-8 feet deep the first year and 16-23 feet the second year. They also release allelopathic chemicals that stunt the growth of many of the surrounding native plants. Over time, Russian knapweed can out-compete and crowd out native plants and form a monoculture.

Known Impacts
Detrimental:
          Allelopathic properties and aggressive competition reduce plant biodiversity. This plant loss reduces forage for a number of wildlife and domestic animals. It is very toxic to horses wet or dry, causing the neurologic disorder named "nigropallidal encephalomalacia". Any cropland invaded by this plant is usually abandoned due to the cost of its control.

Beneficial:
          Young plants may be grazed.

Potential Locations
          Russian knapweed often appears in areas that have a shallow water table (less than 20 feet deep) or that received extra water from irrigation. It invades open sites that have been recently disturbed or heavily grazed. These sites include: cultivated fields, orchards, pastures, roadsides, and rangelands.

Control/Management
          A combination of the following tools is best:
• The most effective management strategy is promoting plant competition. Establish competitive, desired plants in disturbed areas and infested sites. Cool-season perennial grasses have worked well.
• Herbicide has a short-term success, but is not highly effective (example herbicides: Roundup, Tordon 22K,Curtail, Telar [look at herbicide label: free search]).