Shrubs, forming clumps, 7.5-16 cm, sometimes from tuberlike rootstocks. Stem segments not easily detached, dark dull green, often cross wrinkled when stressed, flattened, obovate to circular, 5-11 × 3.5-7.5 cm, fleshy (to flabby and cross wrinkled when stressed), tuberculate, glaucous; areoles 5-6(-8) per diagonal row across midstem segment, oval to subcircular, 2-4 mm diam.; wool tan. Spines (0-)1-4 per areole, usually in distal areoles, erect to spreading, white to red-brown, acicular, straight, terete or 1 flattened, ± stout (0.5 mm diam. at base), longest to 60 mm. Glochids in dense tuft, pale yellow, tan to red-brown, aging brown, to 5 mm. Flowers: inner tepals yellow with red basal portions, 25-40 mm; filaments pale yellow; anthers yellow; style white; stigma lobes cream to yellowish. Fruits green to yellowish to dull red, stipitate, elongate-obovoid, 25-40 × 15-28 mm, fleshy, glabrous; areoles 16-28. Seeds tan, subcircular, 4-5 mm, thickish, warped; girdle broad, protruding to 0.5 mm. 2n = 44. Flowering late spring (May-Jun). Plains, chaparral, grassy woodlands, coniferous forests, sandy to loamy soils; 100-2300 m; Ariz., Ark., Colo., Kans., Mo., N.Mex., Okla., Tex., Utah; Mexico (Chihuahua). Opuntia macrorhiza hybridizes with the hexaploid O. engelmannii (apparently var. lindheimeri) forming the pentaploid O. ×edwardsii V. E. Grant & K. A. Grant. This hybrid is a small subshrub, 20-40 cm, with a mixture of widely spaced, unequal glochids and closely spaced, shorter glochids. Its major spines are gray, and its tepals are yellow or yellow with red bases. Those characteristics are similar to one parent or the intermediate of the two putative parents reported from Blanco and Guadalupe counties, central Texas.
Plant: Erect pad cactus, Clump-formers, to 35 cm tall, sometimes from tuber-like rootstocks. PADS dark green, glabrous, usually glaucous, fleshy to flabby, often cross-wrinkled with stress, obovate to subcircular, 5-11 cm long, 3.5-7.5 cm broad;AREOLES 5-7(-8) in diagonal row across mid-pad, oval to subcircular, 2-4 mm in diameter; wool tan Leaves: SPINES mostly in pads- upper areoles, white to red-brown, the major ones straight, rather stout (ca. 0.5 mm in diameter near base), erect and/or deflexed, (0-)1-4 per areole, the largest 2-6 cm long. GLOCHIDS pale yellow, tan to red-brown, aging brown, forming a well-developed, dense apical tuft, to 6 mm long Flowers: inner tepals yellow with red or reddish bases, 2.5-4 cm long; filaments pale yellow; style white; fresh stigmas yellow. Fruit: FRUITS green, yellowish, to dull red, elongate-obovoid, long-stipitate, spineless, fleshy, 2.5-4 long, 1.5-2.8 cm in diameter; areoles 12-26. SEEDS tan, subcircular, 4-5 mm in diameter, thickish, warped; girdle broad, protruding to 0.5 mm Misc: Sandy to rocky soils, plains, chaparral, grassy woodlands and coniferous forests;; 900-1850 m (2900-6100 ft.); May-Jul REFERENCES: Pinkava, Donald J. Cactaceae. 2003. J. Ariz. – Nev. Acad. Sci. Volume 35(2).