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).

Benson 1982, FNA 2003, Pinkava 2003

Common Name: cactus apple Duration: Perennial Protected Status: Salvage restricted status in Arizona. General: Shrubs- like cactus, 1-3 m tall, from a short trunk which is sometimes decumbent; stems jointed into a series of flattened pads; pads circular to obovate or rhombic, 15-40 cm long by 10-40 cm wide, yellow green to blue green, often glaucous, with areoles in diagonal row across the middle of the pads; juvenile plants have pads that bear long hair-like spines. Spines: Spines usually 1-6 per areole, straight or slightly curved and wider toward the base, the color ranging from white to yellow with red to dark brown at the base, and aging to gray or black; the longest spine at each areole is 1-5 cm long, spreading or reflexed. Each areole also has a scattered yellow to red-brown glochids (fine barbed bristles), of irregular lengths, up to 1 cm long, which turn gray or black with age. Flowers: Petals numerous, yellow to buff but sometimes orange to pink to red, 3-4 cm long; stamens numerous, whitish to cream-colored filaments; style is whitish to cream-colored, topped with a ring of yellow green to green stigma lobes. Fruits: Fleshy, deep red to purple, spineless, and elongate-ovate to barrel shaped, 3-9 cm long by 2-4 cm in diameter, with 20-32 areoles near the top of the fruit; seeds flat and round to triangular, tan to grayish, 2-6 mm long. Ecology: Found on sandy, gravelly, or rocky soils, slopes, bajadas, and flats from 1,000-9,000 ft (305-2743 m); flowers April-July. Distribution: s CA, AZ, NM, TX; south to c MEX. Notes: There are four recognized varieties: var. engelmannii, var. flavispina, var. lindheimeri, and var. linguiformis. Consult Pinkava 2003 for clarification of a variety type. The systematics of this species and O. phaeacantha still appear to remain unresolved, perhaps due to hybridization. The variability of these species is significant and as such other texts should be consulted to clearly distinguish among them. Overall, good characters for easy identification are the larger size of plants, being several segments(pads) tall, the large pads, with generally three visible central spines, often with spines and obvious patches of sparse glochids in areoles over the entire pad; and the consistently golden- yellow flower petals, whereas other species have various colored bases. Ethnobotany: A poultice of the heated plant applied to the breasts was an aid for breast-feeding; the ripe tunas (fruit) are eaten fresh, dried, ground, mixed with corn meal, used as a red dye, fermented for a beverage, and made into a syrup; the tender pads are eaten as nopalitos. Etymology: Opuntia is from Latin root puncti for prickled; engelmannii is named for Georg Engelmann (1809-1884) a German born, American botanical collector. Editor: SBuckley 2010, FSCoburn 2015, AHazelton 2017