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Noxious Weeds


Russian knapweed (Centaurea repens L.)

Sunflower family (Asteraceae) 

Photo collage of Russian knapweed 

GROWTH HABIT:
Russian knapweed is a perennial that is a native of Eurasia, specifically the Caucasus region between the Black and Caspian Seas. Stems are erect, and openly branched on plants that grow 18 to 36 inches (45-91 cm) tall.
LEAVES: Blue green leaves on emerging plants are toothed and covered with fine hairs. Alternately arranged on the stem, the lower leaves are deeply lobed, 2 to 4 inches (5-10 cm) long while the upper leaves are entire or serrate and narrowing to a stalkless (sessile) base. 
FLOWERS:
The cone-shaped flowerheads are 1/4 to 1/2 inch (6 - 12 mm) in diameter and solitary at the tip of leafy branchlets. Pink flowers are common, but may range from white to lavender. Many pearly bracts with rounded or acute papery margins cover the base of the flower (involucre). Flowering occurs from June to September. They are very showy. 
SEEDS:Seeds (achenes) 1/8 to 1/4 inch long (3 to 6 mm), have many white bristles.
OTHER:
Widely established in the western United States, Russian knapweed colonizes cultivated fields, orchards, pastures, roadsides, and wildlands. Propagated by seeds, this weed also forms dense colonies by adventitious shoots from widely spreading black roots. Cultivation, moving infested soils and taking contaminated equipment from place to place spreads this weed. Roots may grow deeply in certain soils.
KEY CHARACTERS:
  • Leaves of newly emerging plants are toothed and covered with fine hair, giving them a blue-green color.
  • Flowers of this perennial are pinkish-purple. Bracts have rounded or pointed papery tips.
Distribution:
Walker, Coleville – Mono County