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Pacific Northwest Research Station
Blue Mountains National Resources Institute

Forestry and Range Sciences Laboratory
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La Grande, OR 97850

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BMNRI Home > Publications > Weeds > Musk Thistle

Publications: Noxious Weeds

Explosion in Slow Motion: A talk by Jerry Asher about noxious weeds in the Blue Mountains

Click on a weed to learn about how to find it and kill it!

Common Crupina
Diffuse Knapweed
Russian Knapweed
Spotted Knapweed
Purple Loosestrife
Perennial Pepperweed
Tansy Ragwort
Medusahead Rye
Rush Skeletonweed
Yellow Starthistle
Canada Thistle
Musk Thistle
Scotch Thistle
Dalmatian Toadflax
Mediterranean Sage
St. Johnswort
Leafy Spurge
Dyers Woad

Wanted: DEAD!

Musk Thistle


  • Leaves: Up to 10 inches long, dark green with a light green midrib, and spiny.
  • Flowers: Large, solitary, purple or deep rose, occasionally white, and nodding. Outer bracts are flat and spreading, ending in spines; inner bracts are narrow and softer. Flowering period starts in June.
  • Seeds: 3/16-inch long shiny yellowish-brown and with a hair-like plume.

Musk thistle is a biennial plant that infests pastures, rangeland, and timberlands, and also roadsides, waste areas, ditch banks, and stream courses. It aggressively forms dense stands, crowding out native species. It spreads by seed.


  • Chemical: Herbicides are effective. Call your local weed control office for the latest methods of eradicating this noxious pest.
  • Biological: An introduced seedhead weevil feeds on the seeds and limits spread.
  • Mechanical: Maintenance of fields and range through fertilization and irrigation helps prevent infestation. Cutting off the rosette below the crown kills the plant, and mowing in bud season can reduce seed production. Burning is *not* advised as it kills the weevils.

Report all sightings to your local Weed Board.

US Forest Service - Pacific Northwest Research Station, Blue Mountains National Resources Institute
Last Modified: Monday, 16 December 2013 at 14:18:43 CST

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