23. Opuntia x occidentalis Engelmann, Proc. Amer. Acad. Arts. 3: 291. 1856 (as species).
Opuntia engelmannii Salm-Dyck ex Engelmann var. occidentalis (Engelmann) Engelmann
Shrubs, sprawling to erect, to 1.5 m. Stem segments not disartic-ulating, green, flattened, obovate, 19-35 × 14-18 cm, ± tuberculate, glabrous; areoles 5-7(-8) per diagonal row across midstem segment, oblong, 5-8 × 4-6 mm; wool dark brown. Spines 3-6 per areole, in most areoles (rarely few spined), spreading, straight, angularly flattened, subulate; abaxial 2-4 spines reflexed, shorter, to 20 mm; adaxial 1-2 spines yellow or white chalky with brown basal portions, 25-50 mm. Glochids in moderately dense crescent at adaxial edge of areole and subapical tuft, reddish brown, to 6 mm. Flowers: inner tepals yellow to deep pink, sometimes darker blush near base, to 50 mm; filaments usually yellow or white; anthers yellow; style pink or white; stigma lobes green. Fruits red-purple throughout, obovoid, 45-50 × 30-40 mm, juicy, glabrous, spineless; areoles 24-30. Seeds yellow-tan, 4-5.5 mm; girdle protruding to 1 mm. 2n = 66.
Flowering spring (Apr-May). Coastal sage scrub, chaparral; 10-500 m; Calif. (including Channel Islands); Mexico (Baja California).
Opuntia ×occidentalis is a hybrid complex involving three, perhaps more, species [at least O. littoralis × (O. engelmannii × O. phaeacantha)]. The hybrids are morphologically variable; the putative parents are all hexaploid. Another similar putative hybrid, O. demissa, probably involves O. oricola (B. D. Parfitt and M. A. Baker 1993).