Origin and Habitat: Mexico(Northern America) in Coahuila, Chihuahua, Durango, and Zacatecas. Big Bend region of Trans-Pecos Texas (USA).
Type locality: Northeastern Zacatecas, Mexico.
Atitude range: Around 600- 1900 metres above sea level.
Habitat and ecology: Various substrates and habitats, desert to mountain grasslands and intermediate slopes. A potential threat to species of the genus Opuntia is the invasion of the cactus moth Cactoblastis cactorum, which can exterminate populations completely

• Opuntia azurea Rose
• Opuntia macrocentra subs. azurea (Rose) Guiggi
• Opuntia violacea var. azurea (Rose) Lodé

• Opuntia azurea Rose
• Opuntia macrocentra subs. azurea (Rose) Guiggi
• Opuntia violacea var. azurea (Rose) Lodé

Description: Opuntia azureaSN|35254]]SN|25100]] is a long-spined, compact, upright, prickly-pear, species with a single trunk and shiny, pale blue-green arms (usually 1-2 m tall), or branching from the base and more or less spreading. Opuntia azureaSN|25090]]SN|25100]] was described as a Mexican species and is characterized by seasonally variable joints, uniformly blue-green or purple at the areoles, that may become uniformly purple in drought or winter. The young spines are usually golden, or reddish, but almost black with age and are borne on the upper part of the cactus. The flowers are beautiful, 3 cm long, rich golden-yellow with a vivid crimson claw; aged flowers turn a pinkish-brown throughout. It produce juicy, edible red/purple fruits.
Derivation of specific name: The specific epithet is after the Latin adjective, azureus, "pure deep blue," in reference to the stem colours of this species.
Stem segments: Joints orbicular to obovate, 10 to 15 cm. in diameter, pale bluish green, glaucous, often purple only at the areoles, if at all (rarely uniformly purple in drought or winter).
Areoles: About 2 cm apart, the lower ones spineless, the upper ones with 1 to 3 rather stout spines. Glochids numerous, dark brown.
Spines: 1-3, unequal, golden, or reddish, almost black with age, the longer ones 2 to 3 cm long, diverging, more or less pointing downward.
Flowers: Intense yellow. Perianth segments c. 3 cm long, deep yellow, with crimson claw, but in age pink throughout; filaments greenish or almost white; stigma-lobes pale green.
Blooming season: Spring ( Mar—May ).
Fruit: Dull crimson, subglobose to ovoid, spineless, truncate, juicy, edible.
Taxonomic notes: Opuntia azurea is an attractive species related to Opuntia chisosensis and Opuntia macrocentraSN|25100]]SN|25090]]. The typical O. azurea is a Mexican taxon with multiple forms and geographic races that closely approaches the international border south of Big Bend National Park in Texas. The taxonomic status of this species is controversial, complex and incompletely understood and O. azurea is considered by some a synonym of the polymorphic, and geographically variable Opuntia phaeacanthaSN|25100]]SN|35254]].
Chromosome number: 2n = 22. O. azurea is diploid, but other ploides exist (e.g., hexaploid), and these probably represent stand-alone species.

Bibliography: Major references and further lectures
1) Hunt, D., Taylor, N. and Charles, G. “The New Cactus Lexicon.” dh Books, Milborne Port, UK. 2006
2) A. Michael Powell; James F. Weedin “Cacti of the Trans-Pecos and Adjacent Areas”. Texas Tech University Press.15 November 2004
3) Orrell T. (custodian) (2016). ITIS Global: The Integrated Taxonomic Information System (version Sep 2015). In: Species 2000 & ITIS Catalogue of Life, 27th February 2016 (Roskov Y., Abucay L., Orrell T., Nicolson D., Kunze T., Flann C., Bailly N., Kirk P., Bourgoin T., DeWalt R.E., Decock W., De Wever A., eds). Digital resource at www.catalogueoflife.org/col. Species 2000: Naturalis, Leiden, the Netherlands. ISSN 2405-8858.
4) N. L. Britton, J. N. Rose: “The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family.” Vol I, The Carnegie Institution of Washington, Washington 1919
5) Joseph Nelson Rose “Studies of Mexican and Central American Plants” Volume 12, Edizione 7 U.S. Government Printing Office, 1909
6) Anderson, E. F. “The cactus family” 2001.
7) Opuntia azurea in: Bradleya: Yearbook of the British Cactus and Succulent Society, Volume 13 page 108 The Society, 1995
8) Cecile Hulse Matschat “Mexican Plants for American Gardens” Houghton Mifflin, 1935
9) Opuntia Web “Opuntia azurea” retrieved 15 March 2016 from <http://opuntiads.com/opuntia-species/opuntia-species-a/opuntia-azurea/>
10) Terry, M., Heil, K., Gómez-Hinostrosa, C. & Corral-Díaz, R. 2013. Opuntia phaeacantha. The IUCN Red List of Threatened Species 2013: e.T152851A686279. http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T152851A686279.en. Downloaded on 16 March 2016.
11) Hernández, H.M., Gómez-Hinostrosa, C. and Goettsch, B. “Checklist of Chihuahuan Desert Cactaceae.” Harvard Papers in Botany 9(1): 51-68. 2004
12) Zimmermann, H.G., M. Pérez-SandyCuen, J. Goluvob, J. Soberón & J. Sarukhán. “Cactoblastis cactorum, una nueva plaga de muy alto riesgo para las Opuntias de México.” Biodiversitas 33(1-6). 2000

Cultivation and Propagation: This is a a much decorative frost hardy cactus easily found in cultivation. It is a summer grower species that offers no cultivation difficulties. Its purple pads provide a striking accent for an otherwise dormant cactus garden.
Soil: Use a very a particularly draining substratum, as it is sensitive to rottenness when in presence of humidity and low temperatures and let the soil dry out between waterings, since it's natural habitat is in sandy or gravelly, well draining soils.
Repotting: Repot in the spring, when their roots become cramped. Generally, they should be repotted every other year in order to provide fresh soil. After repotting, do not water for a week or more.
Water: In summer, during the vegetative period, it must be regularly watered, but allowing the substratum to completely dry up before irrigating again (but do not overwater ); in winter, it’s to be kept dry. Preferable not to water on overcast days, humid days or cold winter days.
Hardiness: It is a quite frost resistant cactus, hardy to -7° C (- 12° C or less if very dry). However in cultivation it is better not to expose it to temperatures lower than -0° C, even if in an aerated and protected location, in order to avoid the formation of anti-aesthetic spots on the epidermis. In presence of high atmospheric humidity avoid any frost as it is particularly sensitive to root rot. USDA Zone 6-10. It can handle extremely high temperatures in summer.
Exposure: Outside full sun or afternoon shade, inside needs bright light, and some direct sun.
Use: It is suitable for small “desert” gardens, in association with other xerophytes. Where the open air cultivation is not possible due to the climate, it is to be cultivated in pot in order to shelter it in winter.
Warning: It is armed with treacherous glochid barbs. All prickly pears have tiny, hair-like glochid thorns in clusters on the pads. The barbed glochids cause extreme discomfort and must be meticulously removed with tweezers.
Propagation: Propagation: scarified seeds, stem division. Prickly pear pads root easily and grow rapidly when placed in loose, well-draining soil.