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squarrose knapweed (Centaurea virgata)
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USDA Symbol: CEVI

ODA rating: A and T
Squarrose knapweed risk assessment
Noxious weed listing process


Distribution
Oregon squarrose knapweed distribution
 
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Images courtesy of Dan Sharratt, Oregon Dept. of Agriculture


If images are downloaded and used from the ODA web site please be sure to credit the photographer.
 
Description
Perennial plant that grows 1 1/2 to 3 feet tall is multi-branched, erect, with many small pink to rose colored flowers. Flowers fall readily from plant stems after flowering and are more slender than most knapweeds, with recurved bract tips. Individual seed heads are deciduous, disloging from the main plant and aiding dispersal by attaching to fur and clothing.
 
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.
 
Distribution in Oregon
The first documented site in Oregon was 1988 in Grant County. Five historic sites have occured in Oregon. Two are currently under management for eradication.
  
 
Biological controls
Biological control agents are not used on "A" listed weeds in Oregon. This weed is being managed for eradication.
 
Informational links
Squarrose knapweed printable trifold(pdf)