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Species
Information
- squarrose
knapweed
- Centaurea
virgata Lam.
- USDA
Symbol: CEVI
- Oregon
Noxious Weed Designation: A,T
- Pictures
ALERT: PLEASE CALL 1-866-INVADER IF YOU SUSPECT YOU HAVE FOUND THIS SPECIES
Identification: Perennial; grows 1 1/2 to 3 feet tall. Multi-branched, erect, with many, small, pink to rose flowers. Flowers fall readily from plant stems after flowering. Flowers more slender than most knapweeds, with recurved bract tips.
Five historic sites have occured in Oregon. Two are currently under management for eradication.
Impacts: Squarrose knapweed is a rangeland and pasture invader, rendering these areas unsuitable for productive grazing. Dispersal is unique among knapweeds because of its habit of breaking off at the base and tumbling across the landscape dispersing seeds along the way. It tends to spread fastest in sheep rangeland.
Individual seed heads are deciduous, disloging from the main plant and aiding dispersal by attaching to fur and clothing.
Biological
Controls: Biological control agents are not used on "A" listed weeds in Oregon. This weed is being managed for eradication.
Oregon
Maps of Squarrose Knapweed Distribution
Links:
USDA
Plants Database information on squarrose knapweed
GRIN
Database information on squarrose knapweed
Oregon Department
of Agriculture information on squarrose knapweed
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