Origin and Habitat: Opuntia stenopetalaSN|33808]]SN|33808]] occurrs widely in Mexico in Coahuila, Nuevo Leon, San Luis Potosi, Tamaulipas, Zacatecas, Queretaro, Hidalgo, and Guanajuato. This species is widespread and abundant.
Type locality: Battlefield of Buena Vista, south of Saltillo, Mexico.
Habitat and Ecology: This cactus grows in xerophyllous scrub and matorral an the Chihuahuan Desert region. Together with Neolloydia conoideaSN|10089]]SN|10089]] and Ariocarpus retususSN|2079]]SN|2079]], Opuntia stenopetalaSN|33808]]SN|33808]] tends to favour limestone, rocky slopes. It is widespread and abundant across its range, and it is not exposed to any major threat. A potential threat to species of the genus Opuntia is the invasion of the cactus moth Cactoblastis cactorum, which can exterminate populations completely. O. stenopetala is pollinated by hummingbirds because of its tubular perianth and red flowers.

• Opuntia stenopetala Engelm.
• Opuntia glaucescens Salm-Dyck

• Opuntia stenopetala Engelm.
• Opuntia glaucescens Salm-Dyck
• Opuntia arrastradillo Backeb.
• Opuntia grandis Pfeiff.
• Opuntia marnieriana Backeb.
• Opuntia riviereana Backeb.

Description: Opuntia stenopetalaSN|33808]]SN|33808]] is a low bushy plant, often forming thickets or mats, the main branches creeping and resting on the edges of the joints. Although in its habit this Opuntia is much like many others, its flowers are unique, the petals being very narrow and erect; it is a very beautiful plant, and at flowering time
is covered with numerous, small, beautiful flowers. Moreover Opuntia stenopetalaSN|33808]]SN|33808]] is a functionally dioecious (unisexual) species. Developmentally, both female and male flowers start out as hermaphrodites, with organ stalling occurring at subsequent stages of their formation. In male flowers, growth and morphogenesis of the gynoecium cease, resulting in the formation of a short style lacking stigmatic tissue and poor ovule development at maturity; while development of the androecium goes on unhindered and large amounts of viable pollen are produced. Conversely, anther development in the female flowers is aborted and no pollen grains are produced. O. stenopetala is one of the most valuable ornamental opuntias.
Stem segments: Joints obovate to orbicular, 10 to 20 cm long, greyish green, but often more or less purplish, very spiny.
Areoles: Often remote, 1 to 3 cm apart, the lower ones often without spines, bearing white wool when young.
Leaves: Only on young joints, spreading, dark red, about 2 mm long.
Spines: Usually reddish brown to black, but sometimes becoming pale, usually 2 to 4, the
longest ones 5 cm long, the larger ones somewhat flattened. Glochids very abundant on young joints, brown.
Flowers: Unisexual, small, including the ovary only 3 cm long; petals orange-red, very narrow, 10 to 12 mm long, with long acuminate tips. Ovary leafy, the upper leaves similar to the sepals. Female flowers with style very thick in the middle bearing 8 or 9 yellow stigma-lobes. Male flowers with an abortive, claviform style, dull pink and yellowish above with the lobules of stigma atrophied and ending in a sharp, rigid tip. Filaments short.
Fruit: Globular, 3 cm in diameter, acid, with or without spines.
Needs: Small, smooth, 3 mm in diameter, with broad, rounded margins.
Chromosome number: n = 11.

Bibliography: Of the six species of Cactaceae described as dioecious, only Opuntia stenopetala, Opuntia grandis and Opuntia glaucescens are dioecious.

Cultivation and Propagation: Major references and further lectures
1) Hunt, D., Taylor, N. and Charles, G. (compilers and editors). “The New Cactus Lexicon.” dh Books, Milborne Port, UK. 2006.
2) Anderson, E. F. “The cactus family” 2001
3) Gómez-Hinostrosa, C., Sánchez , E., Guadalupe Martínez, J. & Bárcenas Luna, R. 2013. Opuntia stenopetalaSN|33808]]SN|33808]]. The IUCN Red List of Threatened Species 2013: e.T152258A615711. http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T152258A615711.en. Downloaded on 17 February 2017.
4) Hernández, H.M., Gómez-Hinostrosa, C. and Goettsch, B. “Checklist of Chihuahuan Desert Cactaceae.” Harvard Papers in Botany 9(1): 51-68. 2004.
5) 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.
6) W. F. Mahler “SIDA, Contributions to Botany”, Volumes 11-12 1985
7) 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
8) Lluvia Flores-Renterıa, Gregorio Orozco-Arroyo, Felipe Cruz-Garcı, Florencia Garcıa-Campusano, Isabel Alfaro and Sonia Vazquez-Santana. “Programmed cell death promotes male sterility in the functional dioecious Opuntia stenopetalaSN|33808]]SN|33808]] (Cactaceae)” Annals of Botany 112: 789– 800, 2013 doi:10.1093/aob/mct141, available online at www.aob.oxfordjournals.org
9) J.A. Reyes-Aguero, J.R. Aguirre R., A. Valiente-Banuet “Reproductive biology of Opuntia: A review” Journal of Arid Environments 64 (2006) 549–585 www.elsevier.com/locate/jnlabr/yjare
10) Marc A Baker, Jon P Rebman, Bruce D Parfitt, Donald J Pinkava, and Allan D Zimmerman “Chromosome Numbers in Some Cacti of Western North America-III” http://www.desertfishes.org/cuatroc/literature/pdf/Pinkava_1977_Chromosome_numbers_cacti_III.pdf
11) B. Goettsch1, H.M. Hernandez “Beta diversity and similarity among cactus assemblages in the Chihuahuan Desert” Journal of Arid Environments 65 (2006) 513–528 http://132.248.13.1/pdf/directorio/h/hernandez_hec/2013/Beta.pdf