Alturas Field Office

Noxious Weeds


Musk Thistle   (Carduus nutans)
Sunflower Family   (Asteraceae)


Musk Thistle
Photo courtesy of the University of Idaho


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Description:  Biennial or winter annual up to 6 feet. Leaves shiny, dark green with a white midrib, hairless, deeply lobed and spiny margined. Leaves extend down stem as spiny wings. Flowers solitary, terminal, nodding, 1-1/2 to 3 inches in diameter, deep rose to violet to purple. Phyllaries broad, spine tipped. Seeds 3/16 inch long, shiny, yellowish-brown, tipped by a tuft of white hairs.

Habitat:  Native to Europe. Invades pastures, rangeleands, forestlands, waterways, meadows, waste areas, and grain fields. This plant can rapidly form dense stands from seed -- 20,000 seeds per plant with 90% viable is common.

Distribution:  The largest known location of musk thistle is found at Mt. Shasta (Siskiyou County). Also found scattered through Dog Valley (Sierra County) and southern Long Valley (Lassen County and Plumas County); and along Highway 395, Interstate 80, Reno, and Verdi along Truckee River (Washoe County, Nevada).

Flowering Period:  June to August