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Species
Information
- spotted
knapweed
- Centaurea
maculosa auct. non Lam. =Centaurea biebersteinii DC.
- USDA
Symbol: CEBI2
- Oregon
Noxious Weed Designation: B,T
- Pictures
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Identification:
Biennial or short-lived perennial; blooms midsummer to fall. Grows up to 3 ft tall. Multi-stemmed plant with several stems arising from crown. Flowers purple or rarely cream colored. Tips of flower head bracts black, thus the name "spotted." Seeds dispersed by wind, animals, and people.
Impacts:
Spotted knapweed is one of the most dominant weed species in the western United States. Millions of acres of prime range and native habitat are infested throughout the northern Rocky Mountain states. Acreage in Oregon is still limited but increasing and has caused economic losses of approximately $54 million dollars in the state. This species will form dense stands on any open ground, excluding more desirable forage species and native plants. On heavily infested range, the necessary control measures to recover the land are often more expensive than the income potential derived from grazing. Control success is hampered by seed longevity. Weeds of the Centaurea genus have more negative impacts to natural and agricultural ecosystems than any other.
Biological
Controls: There are 13 approved biocontrol agents available for release, 12 of which are established in Oregon.
Oregon
Maps of Spotted Knapweed Distribution
Links:
USDA
Plants Database information on spotted knapweed
GRIN
Database information on spotted
knapweed
Oregon Department
of Agriculture information on spotted
knapweed
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