Echinocereus chisoensis

Plants inconspicuous, unbranched or forming small lax clumps. Stems erect or ascending, short cylindric, 12.5-20(-30) × 3-5 cm; ribs (10-)13-16, crests strongly undulate; areoles 5-8.5 mm apart. Spines 11-20 per areole, straight, white, pinkish gray, pale pink, dark brown, or purplish black, tipped brown, central spines darkest (sometimes with annual rings of ± contrasting spine color); radial spines 10-17 per areole, 5-20 mm; central spines (1-)2(-6) per areole, appressed to slightly projecting or spreading, terete, 3.5-17 mm. Flowers 6-9.5 × 5-7 cm; flower tube 10-30 mm; flower tube hairs 3-5(-10) mm; inner tepals white proximally, with basal marks crimson or maroon, bright rose-pink distally, 1.8-5 × 5-16 mm, tips relatively thin and delicate; anthers yellow; nectar chamber 1-2 mm. Fruits green, 15- 35 mm, pulp white. 2n = 22.

Flowering Mar-May; fruiting 2 months after flowering. Chihuahuan Desert, usually sheltered by low, perennial vegetation, desert scrub, gravelly alluvium, bajadas; of conservation concern; 600-900 m; Tex.

Echinocereus fobeanus Oehme, of Mexico, sometimes has been considered a variety of E. chisosensis. Both species seem to be relicts and rare.

Echinocereus chisosensis is in the Center for Plant Conservation´s Collection of Endangered Plants.