squarrose knapweed (Centaurea virgata) ODA rating: A and T
Description
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.
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.
Click on picture to view larger image
Images courtesy of Dan Sharratt, Oregon Dept. of Agriculture
Images courtesy of Dan Sharratt, Oregon Dept. of Agriculture
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. Map legend
Yellow: limited distribution
Red: abundant
Grey: not known to be present
Biological controls
Biological control agents are not used on "A" listed weeds in Oregon. This weed is being managed for eradication.
