Horrid thistle

Cirsium horridulum, the yellow thistle or horrid thistle, is a stout, taprooted biennial or short-lived perennial herb in the Asteraceae, native to eastern and southern North America from coastal Maine and New England south through Florida, west to Texas and Oklahoma, and extending into Mexico, Belize, Guatemala, Honduras and the Bahamas. It develops a basal rosette of pinnatifid, deeply lobed leaves up to 40 cm long armed along the margins and midribs with thick, sharp, yellowish spines. The flowering stem is robust, 30-250 cm tall, woolly, ridged and bears reduced, spiny-margined cauline leaves. Large, broadly hemispheric flower heads 4-7 cm across are borne singly or in small clusters at the stem tips, surrounded by a conspicuous ruff of upper spiny bracts. The disc florets, which lack ray florets, vary remarkably among individuals from creamy white through yellow, pink, lavender, red and purple. Achenes are oblong, slightly compressed, smooth and crowned by a long, plumose pappus that aids wind dispersal.