Plants unbranched. Roots short, obconic taproots; secondary roots diffuse. Stems flat-topped (in old age or under dense brush aerial portion of stem hemispheric), 10 × 8-10(-30) cm, firm; tubercles 8-17 × 4-11 mm; axils bearing (at least seasonally) woolly tufts, wool 3-5 mm, bristles absent; cortex and pith not mucilaginous; latex abundant in healthy tissue throughout cortex of stem, tubercles, and sometimes flower receptacle, sticky, white. Spines (6-)7-8(-10) per areole, white, reddish brown, gray, or yellowish, glabrous; radial spines (5-)6-7(-9) per areole, largest spines reddish brown, gray, or yellowish, tips blackish or dark brown, needlelike, 6.5-13.5 × 0.3-0.6 mm, stiff; central spines (0-)1 per areole, usually ascending and inconspicuous against radial spines, sometimes porrect, straight or slightly curved, largest spines (3-)5-12 × 0.3-0.7 mm; subcentral spines 0. Flowers 2.5-3.5 × 1.9-3.5(-4.4) cm; outermost tepal margins entire; inner tepals white to pale pink, often with pink or lavender midstripes, 8-15 mm; stigma lobes light green, 3-5 mm. Fruits purplish pink, clavate to obovoid, 20-32 mm, juicy only in fruit walls; floral remnant weakly persistent. Seeds reddish brown, 1.1-1.2 mm; pitted; testa leathery to hard, anticlinal cell walls strongly undulate, interstices much narrower than pit diam., pits deeply concave, elongate . 2n = 22.