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Species
Information
- Scotch
thistle (cotton thistle)
- Onopordum
acanthium L.
- USDA
Symbol: ONAC
- Oregon
Noxious Weed Designation: B
- Pictures
Identification:
Biennial that sometimes acts like an annual; blooms in June. Grows 4-8 ft first year. Large amount of soft white hair on upper leaf surface. Towering height, depending on available moisture. Winged tissue along stem. Purple flower. Stands dense and practically impenetrable because of spiny nature and large size. Spreads by seed.
Impacts: Scotch thistle is a wasteland weed that generally inhabits moist sites or drainages in dry locations. If not controlled, it presses into farmland or forms dense canopies in any area overgrazed or not under intense cultivation. It is a major issue in rangeland management in northeastern Oregon.
Biological
Controls: No approved biological control agent is available.
Oregon
Maps of Scotch Thistle Distribution
Links:
USDA
Plants Database information on Scotch thistle
GRIN
Database information on Scotch thistle
Oregon Department
of Agriculture information on Scotch thistle
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