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bull thistle (Cirsium vulgare)
ODA rating: B
 
USDA Symbol: CIVU
Oregon bull thistle distribution
 
Other common names
common thistle and  spear thistle
 
Click on image to view larger photo.
 
Image courtesy of Ken French, Oregon Dept. of Agriculture.

Image courtesy of Eric Coombs, Oregon Dept. of Agriculture

Image courtesy of Ken French, Oregon Dept. of Agriculture
 
If images are downloaded and used from the ODA web site please be sure to credit the photographer.
 
Description
Biennial; blooms July to September and. grows 2 to 5 feet tall.  Many branches sporting green to brown spines and hairs.  Leaves pinnately lobed, hairy, prickly on the upper side and cottony underneath.  Flowers 1 1/2 to 2 inches wide and clustered at ends of branches.  Flowers dark purple.  Seeds topped by a circle of plume-like white hairs.
 
Impacts
A wasteland weed that, if not controlled, presses into farmland.  It is most commonly found in pastures, rangeland, newly logged sites, and takes the place of forbs and grasses..
 
Introduction
Bull thistle is a native of Eurasia and widely established in North America.  It has been accidentally introduced many times through seed contaminant.  Documentation has been found indicating early medicinal uses as well as parts of the plant being edible.
 
Distribution in Oregon
Bull thistle occurs in every county in Oregon.

 
Biological controls
Cheilosia corydon  
Rhinocyllus conicus
Urophora stylata