Scotch thistle USDA PLANTS Symbol: ONAC
U.S. Nativity: Exotic
Habit: Forbs/Herbs
Onopordum acanthium L.
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Taxonomic Rank: Magnoliopsida: Asterales: Asteraceae
Synonym(s): Scottish thistle, cotton thistle, heraldic thistle, Scotch cottonthistle
Native Range: Europe to cent. Asia ()
Scottish thistle is a biennial herb native to Eurasia. Plants can grow up to 8 ft. (2.4 m) tall and 6 ft. (1.8 m) wide. Stems are up to 4 in. (10.2 cm) wide at the base and are marked by prominent, spiny wings along the entire length. Leaves are broadly elliptic, 3.9-19.7 in. (10-50 cm) long, up to 12 in. (30.5 cm) wide with margins marked by large spines. Flowering occurs from July to September, when flowers develop in globe shaped flower heads. Flower heads are purple and up to 2 in. (5.1 cm) in diameter. Fruits are 0.2 in. (4-5 mm) long, smooth achenes. Scotch thistle occurs along roadsides, in fields, pastures, rangelands, riparian areas and other disturbed sites with high soil moisture.
Identification, Biology, Control and Management Resources
Selected Images from Invasive.orgView All Images at Invasive.org


Plant(s);
Richard Old, XID Services, Inc., Bugwood.org
Additional Resolutions & Image Usage
Plant(s); rosette
Richard Old, XID Services, Inc., Bugwood.org
Additional Resolutions & Image Usage
Plant(s); Rosette
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage
Plant(s);
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage

Feature(s); Flower and foliage
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage
Flower(s);
Eric Coombs, Oregon Department of Agriculture, Bugwood.org
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Flower(s);
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage
Plant(s); in flower
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage
Plant(s);
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage
Plant(s);
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage
Infestation;
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage

Infestation; on river bank, seeds travel down water way
Vince Belleci, , Bugwood.org
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Infestation;
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage
Control; Volunteer weed control programs, such as the annual Scotch Thistle Day, help teach young people about the impact of invasive plants on native ecosystems and agricultural production.
Steve Dewey, Utah State University, Bugwood.org
Additional Resolutions & Image Usage
Fruit(s);
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
Additional Resolutions & Image Usage

Diagram or Graphic; Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 3: 556.
USDA PLANTS Database, USDA NRCS PLANTS Database, Bugwood.org
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EDDMapS Distribution:
This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org 		 


State(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.
U.S. National Parks where reported invasive:
Grand Canyon National Park (Arizona)


Invasive Listing Sources:
California Invasive Plant Council
Faith Campbell, 1998
Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
Missouri Department of Conservation,
Pacific Northwest Exotic Pest Plant Council, 1998