Diamond cholla

Opuntia ramosissima Engelmann, Amer. J. Sci. Arts, ser. 2, 14: 339. 1852; O. tessellata Engelmann

Trees or shrubs, intricately branched, 0.5-2 m. Stem segments firmly attached, green drying gray and ropelike, cylindric, 2-8(-10) × 0.4-1 cm; tubercles rhombic, convex (flattened upon drying), 0.4-0.8 cm; areoles subcircular abaxially, adaxially becoming usually deltate-linear; glochid-bearing portion protruding distally, wedged between bases of 2 adjacent tubercles, (3-)4-7 × 1-1.5(-2) mm; wool tan to white. Spines 0-5 per areole, usually in distal areoles or sometimes absent or nearly so, tan to red-brown to deep purple, aging gray; major abaxial spines 0-1(-2), the longest spine spreading, (1.5-)2.5-6 cm; adaxial spines usually reflexed, short to ± 1 cm; sheaths baggy. Glochids in subcircular to linear adaxial tuft, yellow to tan to brown, to 2 mm. Flowers: inner tepals bronze-red ± suffused rose, with mid stripes darker, ovate, 6-13 mm, acute-apiculate to attenuate; filaments greenish; anthers yellow; style whitish or blushed with rose-pink or light green; stigma lobes whitish. Fruits maturing tan, ellipsoid to stipitate-ellipsoid, 15-30 × 10-15 mm, dry at maturity, tuberculate, developing increasingly burlike, with many bristlelike spines; areoles (32-)40-66, evenly spaced, woolly. Seeds pale yellow to tan-gray, angular to squarish in outline, warped, 4-4.5 × 3.5-4 mm, sides irregularly concave-convex; girdle smooth. 2n = 22, 44.

Flowering spring-summer (Apr-Aug). Mojave and Sonoran deserts, washes, flats, and bajadas, sandy loam, desert pavement, stony volcanic substrates; 50-1100 m; Ariz., Calif., Nev.; Mexico (Baja California, Sonora).