Native Range

Southern Europe, the Mediterranean, and Central Asia

Appearance

Plumeless thistle is an upright forb that typically grows as a biennial but can also behave as a winter annual. Plants grow 4 ft (1.2 m) tall on average from a fleshy taproot. Leaves have sharp spines along their wavy, whitish margins. They become more lobed as the plant ages. Stems are erect, highly branched, covered in bristly hairs, and have spiny wings along their entire length. Flower heads are solitary or in small clusters at the ends of stems. They have rows of needle-like bracts and 30–100 pink or purple florets. Seeds are straw-colored and topped by a tuft of fine hairs.

Impact

Introduced thistles currently infest millions of acres across North America, primarily occurring in or along roadways, waterways, agricultural fields, rangelands, pastures, forests, and disturbed areas. They are responsible for millions of dollars of damage annually in reduced agricultural yields and lowered forage value in grazing systems. Introduced invasive thistles can also displace native vegetation, negatively impacting wildlife and threatening the delicate ecological balance within many habitats.

Reference

Randall, C.B., J.E. Andreas, and J. Milan. 2024. Introduced Thistles: History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2024-8- INTRODUCED THISTLES-P. https://bugwoodcloud.org/resource/files/29168.pdf

Resources

• Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service
• Carduus acanthoides - Burke Museum of Natural History and Culture
• Weed Field Guide - USDA Forest Service

Selected Images

Maps

Invasive Listing Sources

• Alberta Weed Control Act
• Arizona Noxious Weeds
• California Invasive Plant Council
• California Noxious Weeds
• Colorado Noxious Weeds
• Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
• Idaho Noxious Weeds
• Indiana Invasive Species Council - Invasive Plant List
• Indiana Terrestrial Plant Rule
• Invasive Plant Species of West Virginia
• Iowa 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.
• Kentucky Exotic Pest Plant Council - Moderate Threat
• Maryland Code and Regulations Noxious Weed & Seed Law
• Maryland Department of Natural Resources Policy: Restriction on Planting Exotic Invasive Plants
• Maryland Invasive Species Council - Invasive Species of Concern in Maryland
• Maryland Noxious Weeds
• Michigan Noxious Weeds
• Minnesota Noxious Weeds
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• Nebraska Noxious Weeds
• New Invaders of the Northwest
• New Invaders of the Southeast
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• North Carolina Noxious Weeds
• Oregon Noxious Weeds
• Pacific Northwest Exotic Pest Plant Council, 1998
• Pennsylvania Department of Conservation and Natural Resources Invasive Plants
• Washington Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• West Virginia Department of Agriculture Regulations Governing the Distribution of Plant Materials
• West Virginia Native Plant Society, Flora West Virginia Project, and West Virginia Curatorial Database System, September 3, 1999
• West Virginia Noxious Weeds
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40
• Wyoming Noxious Weeds

References