Cirsium horridulum, called bristly thistle, purple thistle, or yellow thistle is a North American species of plants in the tribe Cardueae within the family Asteraceae. It is an annual or biennial.100 The species is native to the eastern and southern United States from New England to Florida, Texas, and Oklahoma as well as to Mexico, Belize, Guatemala, Honduras, and the Bahamas.Davidse, G., M. Sousa-Peña, S. Knapp & F. Chiang Cabrera. 2015. Asteraceae. 5(2): ined. In G. Davidse, M. Sousa Sánchez, S. Knapp & F. Chiang Cabrera (eds.) Flora Mesoamericana Universidad Nacional Autónoma de México, México D.F.Carnevali, G., J. L. Tapia-Muñoz, R. Duno de Stefano & I. M. Ramírez Morillo. 2010. Flora Ilustrada de la Peninsula Yucatán: Listado Florístico 1–326Nelson, C. H. 2008. Cat. Pl. Vasc. Honduras 1–1576. Secretaria de Recursos Naturales y Ambiente, TegucigalpaNash, D. L. 1976. Tribe IX, Cynareae. En: Nash, D.L. & Williams, L.O. (eds), Flora of Guatemala - Part XII. Fieldiana, Bot. 24(12): 423–428, 590
Thomas Nuttall (1786–1859) described var. megacanthum as "one of the most terribly armed plants in the genus."Nuttall quoted in Flora of North America, Bigspine thistle, Cirsium horridulum Michaux var. megacanthum (Nuttall) D. J. KeilNuttall, Thomas 1841. Transactions of the American Philosophical Society, new series 7: 421 as Cirsium megacanthum
Description Cirsium horridulum is a biennial herb up to tall, with a large taproot and fleshy side roots that sometimes sprout new shoots. Leaves are up to long with thick, sharp spines along the edges. There are usually several flower heads, also with sharp spines, each head with disc florets but no ray florets. Flower color varies from one plant to the next: white, yellow, pink, red or purple.
Varieties Cirsium horridulum var. horridulum – from Maine to Guatemala Cirsium horridulum var. megacanthum (Nutt.) D.J.Keil – from the Florida Panhandle to Texas and Oklahoma
Cirsium horridulum var. vittatum (Small) R.W.Long – from North Carolina to Louisiana
Conservation status in the United States It is endangered in Connecticut,"Connecticut's Endangered, Threatened and Special Concern Species 2015". State of Connecticut Department of Energy and Environmental Protection Bureau of Natural Resources. Retrieved 12 January 2018. (Note: This list is newer than the one used by plants.usda.gov and is more up-to-date.) New Hampshire, and Pennsylvania. It is listed as threatened in Rhode Island.
As a noxious weed The Cirsium genus is listed as a noxious weed in Arkansas and Iowa.
Native American ethnobotany The Houma people make an infusion of the leaves and root of the plant in whiskey. They use it as both as an astringent, and drink it to clear phlegm from lungs and throat. They also eat the tender, white hearts of the plant raw.Speck, Frank G., 1941, "A List of Plant Curatives Obtained From the Houma Indians of Louisiana", Primitive Man 14:49-75, page 57 The Seminole use the spines of the plant as darts for their blowguns.Sturtevant, William, 1954, The Mikasuki Seminole: Medical Beliefs and Practices, Yale University, PhD Thesis, page 507
Ecology C. horridulum is a facultative upland species that can grow in wetlands, but is usually found in non-wetland ecosystems.USDA, NRCS. (2016). The PLANTS Database (http://plants.usda.gov, 5 April 2019). National Plant Data Team, Greensboro, NC 27401-4901 USA. Its seeds are cypsela that are dispersed by birds and wind. Encyclopedia of Life. Accessed: April 14, 2016
It is a larval host to the little metalmark and the painted lady butterflies.The Xerces Society (2016), Gardening for Butterflies: How You Can Attract and Protect Beautiful, Beneficial Insects, Timber Press. Its flowers are popular for their nectar and pollen with butterflies and bumble bees.
The leaf epidermis is enclosed by both an inner and outer cuticle, which helps minimize the risk of pathogens entering the plant.Pesacreta, T. C. and K. H. Hasenstein (1999). "The Internal Cuticle of Cirsium horridulum (Asteraceae) Leaves." American Journal of Botany 86(7): 923-928.
Cirsium horridulum is insect pollinated and is recorded to have been visited in northern Florida by Agapostemon splendens, Ceratina, Eucera dubitata, and Lasioglossum reticulatum.Ulyshen, M. D., K. Robertson, S. Horn, and C. Dixon. 2024. Characterization of the bee community and pollination network in a southeastern U.S. pine savanna. Frontiers in Ecology and Evolution 12:1403602.
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