Description: Spiny biennial and perennial herbs.
Leaves alternate, entire to pinnatisect usually with spiny teeth on margins.
Heads sessile or pedunculate, solitary or in corymbs; heads globose to campanulate; involucral bracts many-seriate, leathery, tipped with a single spine; receptacle flat to convex, with bristles. Florets all tubular, bisexual, or unisexual and the plants dioecious; corolla 5-toothed, purple or yellowish, rarely white.
Achenes oblong or obovate, compressed, truncate at apex with strong ring of tissue surrounding persistent style base; pappus of numerous, several-seriate, often unequal, plumose bristles united in a ring at the base.
Distribution and occurrence: World: c. 275 species, Europe, Asia & North America. Australia: 4 species (naturalized), all States except N.T.
Text by L. Murray
Taxon concept:
| | Key to the species | |
| 1 | Heads cylindric to narrow-ovoid at flowering, numerous in a corymbose panicle with unisexual florets; upper surface of leaves sparsely cobwebby | Cirsium arvense |
| Heads ovoid, waisted at flowering, solitary or in clusters at the end of main branches with bisexual florets; upper surface of leaves hispid | Cirsium vulgare |
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