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Publications: Noxious Weeds
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!
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
- 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
- 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
- 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