in C. Backeberg and F. M. Knuth, Kaktus-ABC, 126. 1935.
Shrubs or small trees, erect, 0.6–2.5 m. Stem segments easily detached, whorled or subwhorled, green-gray, 4–15 × 3.5–5 cm; tubercles prominent, broadly oval, 1.5–2.5 cm; areoles subcircular to obovate, 4–7 × 3–5 mm; wool tan, aging brown to black. Spines 6–12 per areole, in all but proximalmost areoles, spreading, usually deflexed in abaxial ones, pale redbrown to dark-brown, acicular, the longest to 2 cm; sheaths pale yellowbrown, shiny. Glochids in adaxial crescent and few along margin of areole, yellow to brown, 0.5–2.5 mm. Flowers: inner tepals rose to magenta, to 20 mm; filaments yellow-green to distally tinted pink to magenta; anthers yellow, sometimes bearing stigma-tipped, stylelike appendages; style greenish yellow to often pink distally; stigma lobes yellow to white. Fruits usually sterile, often proliferating into short erect chains of 2–5 fruits, green, broadly ovoid to top-shaped, 21–25 (–35) × 20–32 mm, fleshy, smooth to shallowly tuberculate, spineless; umbilicus broadly shallow, 5–7 mm deep; areoles (20–) 25–35. Seeds rare, globose; girdle smooth. 2n = 22, usually 33.
Phenology: Flowering spring (Apr–Jul).
Habitat: Ocean bluffs, inland coastal sage flats, hills
Elevation: 0–300 m
Calif., Mexico (Baja California)
Cylindropuntia prolifera is of hybrid origin; it occupies a habitat different from its putative parents, C. alcahes (F. A. C. Weber) F. M. Knuth and C. cholla (F. A. C. Weber) F. M. Knuth, two Mexican species.