Knapweed - Acroptilon repens
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Russian knapweed is a bushy rhizomatous perennial, up to 8 dm tall. Stems
and leaves are finely arachnoid-tomentose becoming glabrous and green
with age. The rosette leaves are oblanceolate, pinnately lobed to entire,
2-3 cm wide by 3-8 cm long. The lower cauline leaves are smaller, pinnately
lobed; the upper leaves become much reduced, sessile, serrate to entire.
The heads are numerous terminating the branches. Flowers are pink to purplish,
the marginal ones not enlarged. The outer and middle involucral bracts
are broad, striate, smooth with broadly rounded tips; the inner bracts
are narrower with hairy tips. Pappus present with bristles 6-11 mm long.
Fruit is a whitish, slightly ridged achene.
Russian knapweed is a deep-rooted long lived perennial. Some stands have
been in existence for 75 years. It forms dense colonies in cultivated
fields, orchards, pastures, and roadsides
The plant infests over 600,000 ha in nine western states and 2 Canadian
provinces. It has recently become a problem in winter wheatlands. Once
established, it is difficult to eradicate. It is poisonous to horses causing
Links to more information
Website, video, and graphics by Rob Nelson
For more information on this plant or management please contact US Army Corp of Engineers