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Russian Knapweed

(Acroptilon repens L.)

Russian Knapweed

Russian knapweed is a native of Eurasia, probably introduced to North America about 1898. This plant is considered a noxious weed and is included on the Colorado and the Adams County Noxious Weed Lists. Russian knapweed is an aggressive perennial (lasts several years) weed that reproduces from seed and adventitious buds on a creeping root system.

This plant is allelopathic, which means it exudes toxins into the soil so that no other plant species can grow around it. Dense colonies are usually formed by the widely spreading black, bark-covered roots.Russian Knapweed Root Stems are covered with fine, white hairs that give the stem a blue-green color. Stems are erect, openly branched, with plants standing up to 3 feet tall. Russian Knapweed FlowerFlowers are pink to lavender in color, and are surrounded by pearly, rounded bracts with papery margins that are smooth to the touch.

Russian knapweed invades open, disturbed land, cultivated fields, along ditch banks, fence rows, roadsides, and in waste places. Once established, it tends to form a single-species stand and is very difficult to control or eradicate. Russian knapweed infestations reduce forage for livestock, and greatly reduce biodiversity for wildlife habitat. Plants ingested as fresh or dried forage are toxic to horses, causing a nervous disorder called "chewing disease".

Russian Knapweed Infestation

Approximately 1,400,000 acres in the western United States are infested. Roughly 30,000 of those acres are infested in Colorado.


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