Alturas Field Office

Noxious Weeds



Russian Knapweed   (Acroptilon repens)
Sunflower Family (Asteracea)


Russian Knapweed
Photo courtesy of the University of Idaho


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Description: Perennial forming dense colonies by shoots from widely spreading black roots. Stems erect, openly branched, up to 3 feet. Lower leaves deeply, but not so finely, divided; upper leaves entire or serrate. Flowers 1/4 to 1/2 inch in diameter, numerous on the ends of branches. Ray flowers pink to lavender. Phyllaries pearly, rounded or pointed, with papery margins. Seeds small, from 1/8 to 1/4 inck long, with numerous whitish bristles.

Habitat: Native to central Asia. This weed invades cultivated fields, orchards, pastures, and roadsides, and rangelands. Dense colonies compete with and replace native and desirable vegetation.

Distribution: Russian knapweed is the most widely distributed knapweed in northern California. One of the lagest infestations in an 80 acre site east of Bieber in Big Valley (Lassen County).

Flowering Period: June to September.