Russian Knapweed
(Acroptilon repens)
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MATURE PLANT
* fine hair |
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ROSETTE
* white to lavender color not colorful |
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ROOT
* black in color |
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TOXICITY
* poisonous to horses |
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INFESTATION
* approx…10 acres in El Paso County | |
Russian Knapweed, (Acroptilon repens) is a member of the Aster family, Thistle tribe. It is a perennial and grows up to 3 feet tall. The roots are brownish-black and scaly near the crown. There are numerous branched stems each ending with a flower. The flower is pink-lavender too white. Russian Knapweed flowers in June to August and seeds are produced in later summer to early fall. The seeds are ivory colored and flattened, and are retained in cup-shaped seed heads.
The bulb (involucre) below the blossom is egg-shaped. It is smooth and greenish at the bottom, and is not dotted or sharp.
The leaves are of several types. The upper leaves are small and narrow with unbroken edges. The stem leaves are intermediate in size, with slightly toothed margins. The basal leaves are deeply notched. Short stiff hairs giving the plant an appearance of knap covers the leaves and stems.
The plant spreads by deep creeping roots and seeds. It grows in cultivated fields, along ditch banks, fence rows, roadsides, and in waste places.
It kills other plants and is poisonous to horses.
To control this plant stress the roots by mowing and spraying. Mow at 2 to 3 week intervals over the season followed by fall chemicals. Tilling will produce more plants from buds in the root system. Plant perennial grasses in the fall to help keep noxious weeds from growing back. Fertilize and irrigate the area to stimulate competitive grasses. Russian Knapweed will kill horses if ingested,
Russian Knapweed is a serious noxious weed and is one of four plants that in accordance with the Colorado Weed Management Act, must be managed.