Biennials or perennials, (± fleshy), 15–250 cm; stout taproots and a fascicle of fleshy lateral roots, often perennating by root sprouts. Stems 1–several, usually erect, often stout, glabrous to densely tomentose; branches 0–many, spreading to ascending, short, stout. Leaves: blades linear to oblanceolate or oblong-elliptic, 10–40 × 2–10 cm, unlobed and spiny-dentate to deeply pinnatifid, lobes spiny-dentate or coarsely lobed, main spines stout, 5–30 mm, abaxial faces subglabrous to loosely tomentose, adaxial glabrous to ± densely villous with septate trichomes; basal present at flowering, spiny winged-petiolate, bases often tapered; principal cauline sessile, well distributed, often not much reduced distally, bases often ± auriculate-clasping; distal cauline often spinier than the proximal. Heads 1–20 in subcapitate to corymbiform arrays (each closely subtended by an involucre-like ring of spiny-margined bracts). Peduncles 0–5 cm. Involucres hemispheric to campanulate, 3–5 × 3–8 cm. Phyllaries in 5–9 series, subequal to imbricate, light green to stramineous, lanceolate to linear, distally often with reddish margins, abaxial faces without glutinous ridge, often ± thinly tomentose, often scabridulous in submarginal bands; outer and middle appressed-ascending, bodies usually reddish-tinged, margins setulose-ciliolate, apices acuminate, spines 1–2 mm, weak; apices of inner straight, flat. Corollas white to yellow, pink, purple, or red, 30–47 mm, tubes 11–30 mm, throats 6–10 mm, lobes 7–10 mm; style tips 3–5 mm. Cypselae straw-colored to tan, 4–6 mm, apical collars weakly differentiated; pappi 25–35 mm. 2n = 32, 33, 34, 35.

Distribution

• Generated Map
• Legacy Map

e United States, Mexico.

Discussion

Varieties 4 (3 in the flora).

Although several variants have been given taxonomic recognition as species, these seem at most races. Flower color varies greatly, sometimes within populations and sometimes on a populational or regional basis. Herbarium specimens are sometimes difficult to assign to variety.

Selected References

None.

Lower Taxa

Cirsium horridulum var. horridulum, Cirsium horridulum var. megacanthum, Cirsium horridulum var. vittatum

Key

1	Stems densely tomentose; involucres ± densely tomentose	Cirsium horridulum var. horridulum
1	Stems glabrous or sparsely tomentose; involucres glabrous	> 2
2	Leaves shallowly to deeply pinnatifid, main spines 10–30 mm	Cirsium horridulum var. megacanthum
2	Leaves spinose-dentate to shallowly pinnatifid, main spines mostly 5–10 mm	Cirsium horridulum var. vittatum