Plants usually branched. Roots diffuse; upper portion not enlarged. Stems narrowly cylindric or clavate, 6-15(-30) × (1.5-)2-3.5(-4.5) cm, firm; tubercles 3-5 × 3-5 mm; axils with abundant, persistent, white wool, longest in flowering zone (where exceeding tubercle tips); cortex and pith not mucilaginous; latex absent. Spines (33-)43-60 per areole, white to gray, tan, or pale reddish (central spines with darker, usually chalky blue tips), glabrous; radial spines (27-)37-49 per areole, white or pale tan, bristlelike, 3-6 × 0.05-0.1 mm, stiff, contrasting sharply with robust central spines; central spines 6-12 per areole, straight or weakly recurving throughout their lengths, not hooked, all ± projecting, abaxial and lateral central spines straighter and shorter, 5-8 mm, adaxial central spines 10-15 mm, all 0.2-0.3 mm diam. Flowers 0.9-1.5 × 0.6-1.3 cm; outermost tepal margins toothed; inner tepals maroon-red to rusty red or reddish purple, with paler margins, 4 × 1.5 mm; stigma lobes dull pinkish white to reddish purple or orange-yellow, 1 mm. Fruits bright red, cylindric-clavate, 15-20 mm, juicy only in fruit walls; floral remnant persistent. Seeds light to dark brown, 1-1.2 mm, pitted; testa hard; anticlinal cell walls deeply sinuate; interstices narrower than pit diameters; pits irregularly bowl-shaped. 2n = 22.
|Fox-tail cactus, rat-tail nipple cactus|