Tribe Cynareae Rank Species | Subfamily Carduoideae | |
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Similar Cirsium hookerianum, Cirsium flodmanii, Cirsium brevistylum, Cirsium edule, Cirsium arizonicum | ||
Cirsium horridulum, called bristly thistle, horrid thistle, yellow thistle or bull thistle, is a North American species of plants in the thistle tribe within the sunflower family. 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.
Thomas Nuttall (1786-1859) described var. megacanthum as "one of the most terribly armed plants in the genus."
Cirsium horridulum is a biennial or perennial herb up to 250 cm (100 inches) tall, with a large taproot and fleshy side roots that sometimes sprout new shoots. Leaves are up to 40 cm (16 inches) 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.