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COMMON NAMEScotch thistle FULL SCIENTIFIC NAMEOnopordum acanthium L. FAMILY NAME COMMONAster family FAMILY SCIENTIFIC NAMEAsteraceae IMAGES
NOMENCLATURE/SYNONYMSSynonyms: None DESCRIPTIONOnopordum acanthium is an herbaceous biennial that grows up to 2 m (6.5 ft.) in height or rarely taller. The plant is coarse, many-spined and is highly branched. The stems of Onopordum 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 30 cm (1 ft.) 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 2.5-5 cm (1-2 in.) in diameter. All of the bracts of the involucre are tipped with flat, pale, orange-colored spines. Onopordum acanthium flowers from July to October. The seeds of this plant are 4-5 mm (0.2 in.) long. They are gray in color, and attached to a brown-colored pappus that can be two times as long as the seed. Page References Bailey 1029, Fernald 1543, Gleason & Cronquist 614, Holmgren 584, Magee & Ahles 1022, Peterson & McKenny 302. See reference section below for full citations. SIMILAR SPECIESOther native and invasive thistles
REPRODUCTIVE/DISPERSAL MECHANISMSThe seeds of Onopordum acanthium are dispersed by wind and water, by means of its pappus.
DISTRIBUTIONOnopordum acanthium is native to west, central and southern Europe as well as some parts of Russia. In the United States the plant is found in most states, from Vermont to Virginia, Alabama and Florida and west to California, Oregon, and Washington. In New England this plant has been reported from Vermont, Massachusetts, Connecticut and Rhode Island.
HISTORY OF INTRODUCTION IN NEW ENGLANDThough the actual date of introduction of Onopordum acanthium is unknown, it was most likely introduced in the 19th century as a garden plant. Since it is easily dispersed via wind and water, it likely escaped from gardens onto the landscape.
HABITATS IN NEW ENGLAND,Abandoned Field,Agricultural Field,Edge,Open Disturbed Area,Pasture,Roadside,Vacant Lot,Yard or GardenOnopordum acanthium can still be found in gardens in New England. However, it is more common in agricultural settings, where it is the most problematic.
THREATSOnopordum acanthium is a major agricultural weed in the western United States. If the soil is moist enough, it has the ability to resprout when its roots are cut up during cultivation. This plant spreads easily because each plant can produce over 20,000 lightweight seeds that are dispersed by wind as well as water. The seeds can also be dispersed by becoming attached to livestock. Onopordum acanthium should be monitored in New England in order to avoid it becoming as problematic as it is in many western states. MANAGEMENT LINKS Washington State Noxious Weed Control Board DOCUMENTATION NEEDS Documentation required: A specific photograph or mounted snippet of the flowers, leaves, and/or rosettes.
ADDITIONAL INFORMATION Integrated Taxonomic Information System PLANTS Database Global Invasive Species Database Washington State Noxious Weed Control Board Invasivespecies.gov Field Guide to Noxious and Other Selected Weeds of British Columbia DATA RETRIEVALDataMAPS OF PLANT DISTRIBUTION IN NEW ENGLANDMap
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