Trees, compact, widely branching, 0.4-2 m. Stem segments firmly attached, whorled or subwhorled, green to purple, 5-23 × 1.3-3.5 cm; tubercles crowded, pronounced, oval to narrowly oval, 0.5-1.2(-1.5) cm; areoles broadly obdeltate to elliptic, 4.5-7 × 2-4 mm; wool yellow to tan, aging gray to black. Spines (4-)6-18(-24) per areole, at most areoles, interlacing with spines of adjacent areoles, pale tan (rarely yellowish), pinkish to red-brown; abaxial spines erect to usually deflexed, terete, often flattened basally, 8-19 mm; adaxial spines erect or spreading, subterete; ± bristlelike spines at areole abaxial margins; sheaths persisting, uniformly whitish, not baggy. Glochids in inconspicuous adaxial tuft, yellow to tan, aging gray, 1-2 mm. Flowers: inner tepals rose to red-purple, bronze-purple, or yellow, sometimes pale greenish yellow or whitish, spatulate, 18-35 mm, emarginate-apiculate; filaments deep purple to pink-purple, sometimes green; anthers pale yellow; style white or pink to purple distally; stigma lobes white to cream. Fruits rarely proliferating, yellow, sometimes tinged reddish to purplish, broadly cylindric, 20-50 × 17-30 mm, fleshy, strongly tuberculate, spineless; areoles 28-50(-62); tubercles longer in distal portion of fruit; umbilicus to 10 mm deep. Seeds pale yellow, suborbicular to oval in outline, flattened to warped, 4-5 × 3-4 mm, sides with 0-3 large depressions; girdle smooth. 2n = 22.

Flowering spring-early summer (Apr-Aug). Desert and plains grasslands, extending onto Sonoran Desert flats, sandy to loamy soils; 300-2000 m; Ariz., N.Mex.; Mexico (Chihuahua, Sonora).

Cylindropuntia spinosior forms hybrids with C. acanthocarpa var. major, C. arbuscula, C. fulgida (see 6. C. ×kelvinensis), C. leptocaulis (see discussion under 3. C. ×tetracantha), and C. versicolor (= C. ×grantiorum P. V. Heath). Introgression between C. spinosior and C. imbricata occurs in a more or less continuous band from central New Mexico to Chihuahua, Mexico. The hybrids between C. spinosior and C. acanthocarpa var. major are sprawling shrubs with irregular branching pattern and have spine clusters with one or more spines longer than others and fleshy fruits, some with one to few spines per fruit. Chromosome numbers of hybrids are all reported as 2n = 22.

Plant: compact tree, 0.4-2 m tall, with whorled branches; STEM segments green to purple, 5-23 cm long, 1.3-3.5 cm in diam.; tubercles pronounced, oval to narrowly oval, 4.5-12(-15) mm long. AREOLES yellow- to tan-felty, aging gray to black, broadly obdeltoid to elliptic, 4.5-7 mm long, 2-4 mm wide Leaves: SPINES at most areoles, pale tan (rarely yellowish), pinkish to red brown, interlacing with spines of adjacent areoles, (4-)6-18(-24) spines per areole, 0-few bristly spines at areole basal margins; sheaths uniformly whitish, long-persisting, not baggy; distal spines erect-spreading, subterete; basal spines erect to mostly deflexed, terete, often flattened basally, 8-19 mm long. GLOCHIDS yellow to tan, aging gray, in inconspicuous apical tuft(s), 1-2 mm long Flowers: inner tepals rose to red-purple, or bronze-purple, or yellow, sometimes pale greenish yellow to whitish, spatulate, emarginate-apiculate, 18-35 mm long; filaments deep purple to pink-purple, sometimes green, the anthers pale yellow; style white or pink to purple apically; stigmas white to cream Fruit: yellow, sometimes tinged reddish to purplish, broadly cylindric, pulpy-fleshy, rarely proliferating, 2.5 cm long, 1,7-3 cm in diam., strongly tuberculate, the tubercles increasing in length apically with umbilicus to 10 mm deep; areoles 28-50(-62). SEEDS 4-5 mm long, 3-4 mm wide, pale yellow, suborbicular to oval in outline, nearly flat to warped, the sides smooth with 0-3 large depressions, the girdle smooth, 4-5 mm long, 3-4 mm wide Misc: desert and plains grasslands, extending on to Sonoran Desert flats, sandy to loamy soils; 300-2000 m (1000-6600 ft); Apr-Aug REFERENCES: Pinkava, Donald J. 1999. Cactaceae. Ariz. - Nev. Acad. Sci. 32(1).

Benson 1969, Benson 1892, FNA 2003, Pinkava 1999

Common Name: walkingstick cactus Duration: Perennial Protected Status: Salvage restriced status in Arizona. Spines: Spines 10-20 per areole, spreading in every direction and interlacing with the spines of adjacent areoles, barbed and pale tan or pinkish to red brown with whitish sheaths, they are long persisting but not baggy with basal spines that are erect to mostly deflexed, with distal spines erect-spreading. Flowers: Purplish generally, but color varies considerably, the tepals 4.5-20 mm long and 6-12 mm broad, with small notch at the tip, the anthers are yellow and the style usually purplish. Fruits: Bright lemon yellow berry that is fleshy at maturity, spineless and obovoid but strongly tubercled, 2.5-4.5 cm long, falling off in March. Ecology: Found in desert grasslands, flats, valleys, and plains from 2,000-6,500 ft (610-1981 m), flowers May-June. Distribution: AZ, NM; introduced in Australia. Notes: A medium to large, arborescent, branching cholla distinguished by having stem joints firmly attached to eachother and whorls of short joints growing a right angles to stem; gray to purplish gray spines which do not obscure stems; rose to magenta flowers; spineless fruits with conspicuous tubercles. Ethnobotany: Papago pit baked buds, fruits and joints considered a staple food. Etymology: Cylindropuntia is from Greek kylindros or a cylinder, plus the genus Opuntia, while spinosior is from the Latin for spiny. Synonyms: Opuntia spinosior, O. whipplei var. spinosior Editor: SBuckley 2010, FSCoburn 2015