Trees, with short trunks, openly branched, 3(-5) m. Stem seg-ments 12-40 cm; tubercles widely spaced. Spines and sheaths usually tan to dirty white or ± yel-low, sometimes absent. 2n = 22.

Flowering spring-summer (May-Aug). Deserts, grasslands, pinyon-juniper woodlands, hills, plains; (800-)1100-1800(-2200) m; Ariz., Colo., Kans., N.Mex., Okla., Tex.; Mexico (Chihuahua, Coahuila, Durango, Nuevo León, San Luis Potosí, Tamaulipas, Zacatecas).

Addendum:  Introduced and persisting (but very few in number) in Grand County, Utah (Professor Valley).  Possibly occurring in Utah on the UT-CO line east of Hovenweep National Monument in San Juan County, Utah in a very isolated area which might also involve hybrids with C. whipplei, or which some speculate may have been introduced by pre-Columbian peoples, but seemingly appearing there as if naturally occurring with plants of various ages.  Otherwise, not known from Utah.

A dominant cholla of the Chihuahuan Desert, Cylindropuntia imbricata var. imbricata is wide- ranging and variable in several characters; it is generally shorter and more spiny northward (there often referred to as Opuntia arborescens). The species appears to be spreading northeastward in Oklahoma and Kansas as a result of cattle ranching activities. In Arizona, New Mexico, and Mexico, var. imbricata intergrades with C. spinosior. Northward, var. imbricata hybridizes with C. whipplei (= C. ×viridiflora).

PLANT: Trees to 3 m tall, openly branched. STEM: segments and tubercles large. SPINES: SPINES and sheaths yellowish to usually tan to dirty-white. 2n = 22. NOTES: See also parent taxon. Hills to plains of deserts and grasslands, at times in pinyon-juniper woodlands; -Gila, Pima, cos.; 800-2200 m (2700-7300 ft); May-Aug; CO, KS, NM, OK, TX; n Mex. Cylindropuntia imbricata var. imbricata is the wide-ranging aspect-dominant cholla of the Chihuahuan Desert; AZ specimens poorly represent the species (probably introgressed). Hybridizes with C. whipplei and occurs in scattered localities (perhaps transported by Native Americans) in n NM, sw CO and Navajo Co., AZ, this hybrid, C. viridiflora (Britton & Rose) Knuth, having a low, bushy habit, ripe cantaloupe-colored inner tepals, and an irregular non-dimorphic spine pattern, 2n = 22. REFERENCES: Pinkava, Donald J. 1999. Cactaceae. Ariz. - Nev. Acad. Sci. 32(1).