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

Original Description

What is Opuntia azurea?

Opuntia azurea is an attractive prickly pear cactus from the Big Bend Region of Texas and adjacent Mexico that is related to O. macrocentra. Many of the varieties are purple, especially in winter.

Details

A full technical description of this Opuntia and its proposed varieties begins on page 130 of The Cacti of the Trans-Pecos and Adjacent Areas (Powell and Weedin, 2004).

Powell and Weedin described five varieties of O. azurea.

aureispina
azurea
discolor
diplopurpurea
parva

We recognize a sixth possible variety of Opuntia azurea that remains undescribed and provisionally designate it as O. azurea var. casteretti. This variant is characterized primarily by white spines and may represent merely a white-spined form of O. azurea var. diplopurpurea. Powell and Weedin (date) previously considered such white-spined plants to be variants of O. macrocentra, without taxonomic distinction.

Cytological reports on O. azurea vary, indicating tetraploid or hexaploid chromosome counts. While it is conceivable that ploidy level might differ among varieties, there is currently no supporting evidence for such variation within this species.

Other Notes

This Opuntia species is widely distributed, extending into Mexico, and exhibits considerable morphological variability. Depending on the variety, the base of the cladodes may display purple pigmentation, or the entire cladode may turn purple during winter months. Spine morphology varies from slender to robust among varieties. Additionally, plant height is a distinguishing feature, with some varieties reaching 1 meter or taller, while others remain shorter than 1 meter. Cladode size also serves as a useful character for differentiating varieties within this species.

The Flora of North America Online does not recognize this taxon.

O. azurea is cold-hardy and attractive in any collection.

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