Shrubs or trees, with short trunk , spreading to sometimes de-cumbent, 1-3 m. Stem segments not disarticulating, yellow-green to blue-green, flattened, circular to obovate to rhombic, or apex tapering, elongate, 15-40(-120) × 10-40 cm, ± tuberculate, gla-brous, often glaucous; areoles 5-8 per diagonal row across mid-stem segments, evenly distributed on stem segment to absent, subcircular to obovate, 4-7 × 4-6 mm; wool tawny, aging blackish. Spines (0-)1-6(-12) per areole, white to yellow, usually red to dark brown at extreme bases, aging gray to ± black, subulate, straight to curved, flattened to angular at least near base, the longest spreading to strongly reflexed, 10-30(-50) mm. Glochids widely spaced, sparse in crescent at adaxial edge, encircling areole or nearly so, and scattered in subapical tuft, yellow to red-brown, aging gray to blackish, of irregular lengths, to 10 mm. Flowers: inner tepals uniformly yellow to buff, sometimes orange to pink to red (rarely whitish), 30-40 mm; filaments, anthers, and style whitish to cream; stigma lobes yellow-green to green. Fruits dark red to purple throughout, sometimes stipitate, ovate-elongate to barrel-shaped, 35-90 × 20-40 mm, juicy (bleeding and staining), glabrous, spineless; areoles 20-32 usually toward apex. Seeds tan to grayish, subcircular to deltoid, flattened, 2.5-6 × 2-5 mm; girdle protruding 0.3-0.5 mm. The basal portions of stems seedlings of Opuntia engelmannii bear long hairlike spines. The name Opuntia dillei Griffiths has been used for a spineless or nearly spineless morphotype of O. engelmannii.

Plant: tree or shrub, short trunk, spreading to sometimes decumbent, 1-3 m tall. PADS yellow-green to blue-green, glabrous, often glaucous, circular to obovate to rhombic, or (in var. linguiformis, the apex tapering, elongate), 15-40(-120) cm long, 10-40 cm broad; JUVENILES with pad bases bearing long hair-like spines. AREOLES 5-8 in a row diagonal across midpads, subcircular to obovate, 4-7 mm long, 4-6 mm wide; wool tawny, aging blackish Leaves: SPINES evenly distributed on pad to absent, white to yellow, usually red to dark brown at extreme bases, aging gray to ± black), subulate, straight to curved, flattened to angular at least at base, (0-)1-6(-12) per areole, the largest spreading to strongly reflexed, 1-3(-5) cm long. GLOCHIDS yellow to red-brown, aging gray or blackish, widely spaced, of irregular lengths to 12 mm long, in apical crescent and encircling the areole or nearly so, and scattered in subapical tuft Flowers: inner tepals of uniform color, yellow to buff, sometimes orange to pink to red, rarely whitish, 3-4 cm long; filaments and style whitish to cream-colored; fresh stigmas yellow-green to green Fruit: deep red to purple throughout, elongate-ovate to barrel-shaped, sometimes stipitate, spineless, juicy (bleeding and staining), 3.5-9 cm long, 2-4 cm in diameter; areoles 20-32, mostly toward apex. SEEDS tan to grayish, subcircular to deltoid, flat, 2.5-6 mm long, 2-5 mm wide; girdle protruding 0.3-0.5 mm. REFERENCES: Pinkava, Donald J. Cactaceae. 2003. J. Ariz. – Nev. Acad. Sci. Volume 35(2).