5. Grusonia kunzei (Rose) Pinkava, J. Arizona-Nevada Acad. Sci. 32: 50. 1999.
Opuntia kunzei Rose, Smithsonian Misc. Collect. 50: 505. 1908; Corynopuntia stanlyi (Engelmann ex B. D. Jackson) F. M. Knuth var. kunzei (Rose) Backeberg; C. stanlyi var. wrightiana (E. M. Baxter) Backeberg; Grusonia wrightiana (E. M. Baxter) E. M. Baxter; O. stanlyi Engelmann ex B. D. Jackson var. kunzei (Rose) L. D. Benson; O. stanlyi var. peeblesiana L. D. Benson; O. wrightiana (E. M. Baxter) Peebles
Shrubs, forming mats, to 50 cm, in series of usually 2-4 stem segments. Roots diffuse. Stem segments curved and narrowed at base, 10-15 × 2.5-4 cm; tubercles prominent, 20-30 mm, narrow, 4-6 times longer than wide, obscured by interlacing spines; areoles 5-6 mm in diam.; wool gray-white. Spines 17-27 per areole, ± uniformly distributed along stems; major 4-6 abaxial spines deflexed, tan with whitish margins, strongly flattened, longest to 4.5 cm; major 4-5 adaxial spines divergent, tan to reddish tan, angled at base, longest subterete, to 5 cm. Glochids few in adaxial portion of areole, yellow, 5-6 mm. Flowers: inner tepals yellow to pale yellow-green, to 15-20 mm; filaments white; style light green to white; stigma lobes white. Fruits sometimes proliferating, lemon yellow to yellow, 40-75 × 15-40 mm, fleshy, very spiny, glochidiate; spines (4-)6-17 per areole, straw yellow to brown, 12-20 mm, retrorsely barbed; areoles (40-)45-70. Seeds yellowish white, 4-5 × 3.5-4.5 mm, smooth. 2n = 44.
Flowering spring (Apr-Jun). Sonoran Desert, silty, sandy, or gravelly flats and hills; 200-600 m; Ariz.; Mexico (Baja California, Sonora).