Opuntia azurea, Purple Pricklypear

Rose, Contributions from the U.S. National Herbarium 12(7): 291, 1909

Holotype; Isotype; Isotype; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium (O. azurea diplopurpurea); Holotype (O. azurea diplopurpurea); Holotype (O. azurea discolor); Herbarium (O. azurea discolor); Herbarium (O. azurea parva); Herbarium (O. azurea parva); Herbarium (O. azurea parva); Herbarium (O. azurea parva); Painting (possible O. azurea); O. azurea castetteri; O. azurea castetteri; O. azurea castetteri

See O. chisosensis
See O. macrocentra

Original Description

What is Opuntia azurea?

Opuntia azurea is an attractive prickly pear from the Big Bend region of Texas and adjacent Mexico, closely related to O. macrocentra. Many plants and named varieties develop purple pads in winter.

Details

Shrubs: compact to upright, sometimes with a single trunk, about 1–2 m tall. Cladodes: orbicular to obovate, c. 10–15 cm in diameter, pale bluish-green and glaucous. Areoles: about 2 cm apart. Glochids: numerous, brown. Flowers: deep yellow, c. 3 cm long, with a crimson claw; in age the petals may be pink throughout. Fruits: dull crimson, subglobose to ovate, truncate, spineless; pulp light-green, juicy, and edible. Spines: lower areoles without spines; upper areoles with 1–3 more or less reflexed spines, almost black at least when old; spines unequal, the longer 2–3 cm. Filaments: greenish to almost white. Anthers: pale yellow. Stigmas: pale green.

Varieties recognized here: aureispina, azurea, discolor, diplopurpurea, parva. A white-spined castetteri expression is shown and may represent a pale-spined form within O. azurea var. diplopurpurea rather than a distinct taxon.

Cytology

Reports vary for O. azurea, indicating tetraploid or hexaploid counts; differences among varieties are conceivable but unconfirmed.

Other Notes

Plants range from sprawling to somewhat tree-like and vary in spine thickness and the extent of purple pigmentation on pads (confined to the base in some plants or suffusing entire cladodes in winter). Cladode size is useful for distinguishing varieties. The taxon is widely distributed into northern Mexico. The Flora of North America Online does not recognize this taxon. Cold-hardy and striking in cultivation.