Synonym(s): Carduus lanceolatus, Carduus vulgaris, Cirsium lanceolatum
Family: Asteraceae (Aster Family)
Duration and Habit: Biennial Herb
Bull thistle is a biennial, and sometimes annual or monocarpic perennial, forb. In the juvenile phase, individual bull thistle plants form a single rosette with a taproot up to 28 inches (70 cm) long. Rosettes may develop up to 3.3 feet (1 m) in diameter. The taproot does not spread, but develops several smaller lateral roots. Stems have spiny wings and grow 1 to 6.6 feet (0.3 to 2 m) tall, with many spreading branches, and sometimes a single stem. Bull thistle stem leaves are more or less lance-shaped and 3 to 12 inches (7.6-30 cm) long, prickly hairy on the top and very hairy underneath. Lobes on leaves are tipped with stout spines. Bull thistle flowerheads are 1.5 to 2 inches (3.8 to 5 cm) in diameter, 1 to 2 inches (2.5-5 cm) long, usually solitary, and more or less clustered at the ends of shoots and branches. Flowers are subtended by narrow, spine-tipped bracts. Bull thistle fruits are achenes, 1/16th-inch (0.15 cm) long, with a long, hairy plume that is easily detached.
Ecological Threat: Bull thistle is a problem in pastures because it competes with and decreases desirable forage and has no significant nutritive value for livestock. Sharp spines deter livestock, and presumably wildlife, from grazing. It is regarded as a serious pest in protected areas and parks such as Yosemite, Yellowstone, Teton and Glacier National Parks.
Biology & Spread: Seed production and seedling establishment are often enhanced under disturbed conditions, which create open, habitable sites for invasive species. A comparison of bull thistle demography in grazed and ungrazed pastures in Australia found that plants produced nearly 3 times as much seed on average in heavily grazed pasture (33 flowerheads per plant and 198 seeds per flowerhead) compared to ungrazed pasture (19 flowerheads per plant and 149 seeds per flowerhead) when averaged over 3 years.
History: Native to Europe, from Britain and Iberia northward to Scandinavia, eastward to western Asia, and southward to northern Africa. It is found on every continent except Antarctica, although its distribution is confined mostly to the northern and southern temperate zones.
U.S. Habitat: Roadsides, pastures, and waste places.
U.S. Nativity: Introduced to U.S.
Native Origin: Europe, w. Asia, N. Africa (Bailey, L.H. and E.Z. Bailey, Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada, MacMillan Publishing Co., Inc., New York , (1977).); NatureServe Explorer
U.S. Present: AK, AL, AR, AZ, CA, CO, CT, DE, FL, GA, HI, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY
Distribution: Throughout North America, except parts of far north.
List All Observations of Cirsium vulgare reported by Citizen Scientists
The key to successful management of bull thistle is to prevent seed production.
Physical/mechanical: Any mechanical or physical method that severs the root below the soil surface will kill bull thistle plants. However, it is essential to re-vegetate the site with desirable plants to compete with bull thistle that may reinvade from seeds left in the soil.
USFS. 2008. Fire Effects Information Center. Cirsium vulgare. Accessed 19 November 2008: http://www.fs.fed.us/database/feis/plants/forb/cirvul/all.html.
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