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Pacific Northwest Research Station
Blue Mountains National Resources Institute

Forestry and Range Sciences Laboratory
1401 Gekeler Lane
La Grande, OR 97850

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BMNRI Home > Publications > Weeds > Russian Knapweed


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
Puncturevine
Tansy Ragwort
Medusahead Rye
Rush Skeletonweed
Yellow Starthistle
Canada Thistle
Musk Thistle
Scotch Thistle
Dalmatian Toadflax
Mediterranean Sage
St. Johnswort
Leafy Spurge
Whitetop
Dyers Woad

Wanted: DEAD!

Russian Knapweed

Alias: Turkestan thistle

  • Stems: Up to 3 feet tall and branched
  • Leaves: Lower leaves long, generally lobed; Upper leaves smaller, toothed or entire. Leaves are 6 inches long at base, and get smaller toward top of plant
  • Flowers: Flowering heads are narrow, flowers are about 1/2-inch wide, pink to lavender. Flowering period is from June to September.
  • Seeds: Ivory colored, obscurely striped, 1/8-inch long, at first tipped with bristle tuft of unequal length.

Russian knapweed is a woody perennial that can form dense colonies. The entire plant is more or less white woolly when young. It infests alfalfa and grain fields, irrigation ditches, and waste areas. It spreads by seed and rootstock and can produce up to 27 root shoots a year. The deep, extensive root system (up to 23 feet) makes it especially difficult to control. It emits a substance that inhibits the growth of other plants around it. The leaves are bitter and unpalatable to livestock. Causes "chewing disease" (trachea paralysis) in horses.


***WARNING: All knapweeds may contain a cancer-causing agent.***

***Handle with extreme caution!***


Control:

  • Biological: Sheep graze the new growth while it is succulent, but this is not particularly effective. Reseeding with fast-growing grasses can prevent new invasions. Seedhead flies can reduce it a bit.
  • Mechanical: Continuous tillage combined with herbicide application can be effective. Otherwise, tillage or pulling only serves to spread it. Wear gloves when pulling!
  • Chemical: Most effective application is during the early bud stage. Consult your Weed Board for more details.

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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