Native Range

Europe, Western Asia, and the Mediterranean

Appearance

Yellow starthistle is an herbaceous winter annual typically growing 1–3 ft (30–90 cm) tall from a deep taproot. Rosettes have deeply lobed leaves up to 6 in (15 cm) long. Plants produce one or more rigid, upright stems with multiple spreading and ascending branches. Stem leaves are typically narrow, unlobed, and attach directly to plant stems by wings that run down the sides of the stems. All stems, leaves, and wings are covered in densely matted hairs, resulting in a characteristic gray-green color. Flower heads are produced at tips of branches, and sometimes at leaf or branch axils. Flower heads are up to ¾ in (2 cm) across and consist of 10– 80 bright yellow florets. The bracts are spiny and up to 1 in (2½ cm) long. Seeds are oblong and up to [ in (3 mm) long. Plumed seeds are tan to brown, located at the center of the seed head, and have a ring of pappus consisting of fine, white bristles. Plumeless seeds are dark brown to black, fewer in number, occur around the periphery of the seed head, and lack pappus.

Impact

Yellow starthistle is one of the most problematic introduced plant species currently threatening conservation areas and rangeland in the western USA. It reduces biodiversity by displacing native vegetation in grasslands and woodlands. The thorny spines that surround starthistle flower heads interfere with grazing by livestock and wildlife as well as recreation. It is toxic to horses, causing a chronic and potentially fatal neurological disorder known as “chewing disease”. Because of its excessive water usage, yellow starthistle threatens both human economic interests and native plant ecosystems.

Reference

Randall, C.B., L. Smith, and J. Milan. 2023. Yellow Starthistle (Centaurea solstitialis): 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-2023-14-YELLOW STARTHISTLE-P. https://bugwoodcloud.org/resource/files/27954.pdf

Resources

• Biology and Biological Control of Yellow Starthistle - USDA Forest Service
• Weeds Gone Wild: Alien Plant Invaders of Natural Areas - Plant Conservation Alliance
• Element Stewardship Abstract - The Nature Conservancy
• Weed of the Week - USDA Forest Service
• 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
• Idaho Noxious Weeds
• Invasive Plant Species of West Virginia
• Iowa Forest Invasive Plants
• 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.
• Minnesota Noxious Weeds
• Montana Noxious Weeds
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• Nevada EDRR
• Nevada Noxious Weeds
• New Mexico Noxious Weeds
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• Ontario’s Invading Species Awareness Program Tracked Species List
• Oregon Noxious Weeds
• Pacific Northwest Exotic Pest Plant Council, 1998
• Utah Noxious Weeds - Control
• Washington Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• West Virginia Native Plant Society, Flora West Virginia Project, and West Virginia Curatorial Database System, September 3, 1999
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40
• Wyoming Noxious Weeds

References