- Onopordum acanthium is an herbaceous biennial plant that can grow up to about 6.5 ft. (2 m) in height. The plant is coarse, many-spined and is highly branched. The stems of O. acanthium are winged. The whole plant is densely tomentose, giving it a bluish-white appearance.
- The leaves are oblong and prickly, being toothed or slightly lobed along the margins. The apex of the leaf is acute. The leaves are mostly sessile, with some of the lower leaves having petioles. The blades of the lower leaves can measure up to 1 ft. (30 cm) long. Since this plant is a biennial, only the basal rosette of leaves is present in the first year of its growth.
- The flower heads are purple and measure 1-2 in. (2.5-5 cm) in diameter. All of the bracts of the involucre are tipped with flat, pale, orange-colored spines. Flowering occurs from July to October.
- The seeds of this plant are 0.2 in. (4-5 mm) long. They are gray in color, and attached to a brown-colored pappus that can be two times as long as the seed.
- Ecological Threat
- O. acanthium is a major agricultural weed in western United States. With enough moisture, it can resprout from roots cut up during cultivation. This plant spreads easily because each plant can produce over 20,000 wind dispersed seeds. The seeds can also be dispersed by water or by being caught in the fur of animals.
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EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org
State Invasive List - This map identifies those states that list this species on their invasive species list. For more information, visit Invasive.org
Invasive Listing Sources
- Arizona Noxious Weeds
- California Invasive Plant Council
- California Noxious Weeds
- Connecticut Invasive Plant List
- Faith Campbell, 1998
- Great Lakes Early Detection Network
- Idaho Noxious Weeds
- 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,
- Missouri Noxious Weeds
- Nevada Noxious Weeds
- New Mexico Noxious Weeds
- Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
- Oklahoma Noxious Weeds
- Oregon Noxious Weeds
- Pacific Northwest Exotic Pest Plant Council, 1998
- South Dakota Noxious Weeds
- Utah Noxious Weeds
- Washington Noxious Weeds
- WeedUS - Database of Plants Invading Natural Areas in the United States
- Wyoming Noxious Weeds
Other System LinksPlants: ONAC
NPDN Pest: PBFCNBA
NPDN Host: 36437
|Common Name Reference:|| Weed Science Society of America Common Names List|
|Scientific Name Reference:||USDA, NRCS. 2010. The PLANTS Database. National Plant Data Center, Baton Rouge, LA, USA.|