Cirsium arizonicum var. rothrockii (A.Gray) D.J.Keil

Stems glabrous. Leaf blades ± deeply divided or the distal unlobed and merely spiny-dentate, faces glabrous or the basal abaxially sometimes thinly tomentose, rarely with septate trichomes abaxially along the midveins; main marginal spines often stout, 5–15 mm; cauline bases usually narrowed, not decurrent. Involucres cylindric to narrowly ovoid. Phyllary spines slender to very stout, 5–30 mm. Corollas bright red, 28–32 mm, tubes 10–12, throats 1.5–3 mm, lobes 15–17 mm; style tips 1–2.5 mm. 2n = 30 (as C. rothrockii).