Opuntia azurea, Texas prickly pear cactus, blue plant

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)

See O. chisosensis

See O. macrocentra

What is Opuntia azurea?

Opuntia azurea is an attractive prickly pear cactus from the Big Bend Region of Texas that is related to O. macrocentra. A full technical description of this Opuntia appears on page 130 of The Cacti of the Trans-Pecos and Adjacent Areas (Powell and Weedin, 2004).

Details

The cladodes are glaucous blue-green, and areoles are 1.2 to 1.6 cm apart. When mature, spines are black, unequal, and up to 2.5 cm long. Flowers are yellow with red centers, essentially identical to those of O. macrocentra. Stigmas are pale green. This Opuntia is a wide-ranging (into Mexico) and variable species. The Flora of North America does not recognize this taxon.

Powell and Weedin described five varieties of O. azurea.

aureispina
azurea
discolor
diplopurpurea A.M. Powell & J.F. Weedin
parva A.M. Powell & J.F. Weedin

We include a sixth possible variety of this prickly pear that is undescribed. We provisionally refer to it as O. azurea casteretti. Perhaps it is only a white-spined version of another Opuntia variety, O. azurea diplopurpurea. Powell and Weedin considered these white-spined plants to be variants of O. macrocentra and nothing more. See the original description. O. azurea is tetraploid or hexaploid depending upon the report. Perhaps (not sure) polidy varies with variety.

Depending upon the variety, the plant may be purple at the cladode base or may turn entirely purple in winter. Spines may be slender or robust. Also varieties are differentiated by height with some 1 m or taller and others less than 1 m. Additionally, cladode size may differentiate varieties.