Shrubs, branching basal, 3-6[-12+] m. Stems erect, at first yellow-green then green, lacking red pigmentation, glabrous and dull, forming patches of orange young bark on aged and undamaged segments; ribs [12-]15-19, somewhat tuberculate, interareolar transverse fold often present on young ribs, 9-12 mm to rib crest; cortex yellowish, mucilage sacs conspicuous in outer cortex only; pith lacking mucilage, 4-6 cm wide; areoles 1-1.6 cm apart along ribs, circular, 4-6 mm, hairs reddish brown. Spines 11-14(-19), thin, straight; radial spines 1-3.5 cm; central spines to 6 cm. Flowers nocturnal, mostly subterminal, funnelform, to 6-7.5(-9) × 6-7 cm; flower tubes about 4 cm; scales at base of tube red with green margins; tepals to 6.5 cm wide; outer tepals reddish with pink margins; inner tepals cream-white to light pink; filaments white to pink, 2-3 cm; ovary tuberculate with green, rhomboid tubercles and small red bracts at anthesis, areoles with tan hairs and sometimes short spines; styles white, 4 cm; nectar chamber 1-1.5 cm. Fruits red, 45-65 mm, fleshy, bearing deciduous spiny areoles; pulp sweet. Seeds 2 mm, glossy. 2n = 22. Flowering (Mar)Apr-Jul[-Dec]; fruiting mostly Jul-Aug. Upland Sonoran desert scrub; 20-1100 m; Ariz.; Mexico (Baja California, Baja California Sur, Sinaloa, Sonora). Stenocereus thurberi is a common columnar cactus of the Sonoran Desert, throughout Baja California and the islands of the Gulf of California and in the west-coastal vegetation from Sonora to Sinaloa. In Mexico, where S. thurberi is arborescent, it has a very short trunk to 0.5 m, exceeds 12 m, branches more than in northern populations, and can have as few as 12 ribs. Tall specimens of S. thurberi occur where the plants grow in taller vegetation, hence competing with small trees for sunlight (A. C. Gibson and P. S. Nobel 1986). Stenocereus thurberi belongs to the largest clade of Stenocereus wherein all species possess dark red or brown, glandular areolar trichomes (A. C. Gibson 1988). The group of species most closely related to S. thurberi have the interareolar transverse fold, a distinctive mark that persists after the ribs become fully expanded.

Plant: Shrubs to 6 m tall. STEM much branched from the base, sometimes rebranched above, erect, green, the branches to 12-20 cm in diameter; ribs (12-)15-17(-20), 9-15 mm high. AREOLES subcircular, 4-6 mm in diameter, ca. 1-2 cm apart on rib, mostly red-brown woolly, aging gray Leaves: SPINES red-brown, coated whitish, aging gray with dark tips, terete, mostly bulbous-based, divergent; central-most spines 3-5 per areole, slender, the longest 17-32 mm long; peripheral spines 6-11, finer, 1-2 cm long Flowers: mostly subterminal, funnelform, 6-9 cm long, 3.5-6 cm wide; floral tube 2-4.5 cm long; outer tepals green, tinged red or rose-red to purplish, obovate; inner tepals white aging lavender or rose-pink with white margins, reflexed, oblong, to 2 cm long, 7 mm broad; stamen filaments cream-white, the anthers yellowish; style white; stigma lobes ca. 9, white Fruit: FRUITS reddish with green scales, glabrous, with deciduous spiny areoles, globose, 3-5(-6.5) cm long and wide; pulp juicy, red, sweet. SEEDS black, glossy, finely pitted, obovate, ca. 2 mm long and 1.2 mm wide REFERENCES: Pinkava, Donald J. 1995. Cactaceae. J. Ariz. – Nev. Acad. Sci. 29(1): 2, 6.