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Italian thistle (Carduus pycnocephalus)
ODA rating: B
 
USDA thistle: CAPY2
Oregon Italian thistle distribution
 
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 Image courtesy of Ken French, ODA
 
Image courtesy of Eric Coombs, ODA
Image courtesy of Dan Sharratt, ODA
 
Description
Annual or sometimes biennial; blooms May to June. Grows 1 to 4 ft tall. Stems have spiny wings. Leaves deeply cut into 2 to 5 pairs of lobes, have white spots and undersurface slightly woolly. Flowers purplish to pinkish, borne in cylindrical heads either solitary or in clusters of more than 5. Bracts hairy. Fruits from outer part of flower head are gray in color and inner portion are yellowish to tan.
 
Impacts
Italian thistle is native to southern Europe. It infests roadsides and waste areas, and has become a major problem on hill pasture land in Douglas County, Oregon. Once established, it spreads rapidly and forms dense stands which displace more desirable vegetation and exclude livestock.
 
Distribution in Oregon
First record of this plant in Oregon was 1929 in Lane County.

Biological controls
Two approved biocontrol agents, a seed head weevil and a stem-boring fly, have been successfully established in Oregon.