Below is an excerpt from the New Mexico Rare Plant Website.
Opuntia viridiflora (Santa Fe cholla)
Family: Cactaceae
Scientific Name: Opuntia viridiflora Britton & Rose
Synonyms: Cylindropuntia viridiflora (Britton & Rose) Knuth; Opuntia imbricata Haworth var. viridiflora D. Weniger [comb. illeg.]; Opuntia whipplei var. viridiflora (Britton & Rose) L. Benson.
Vernacular Name: Santa Fe cholla
Description: Plants shrubby, much-branched to about 0.8 m in height and about 2 meters across; main stems with lateral "joints" primarily in whorls at ends of each year's growth, Flowers 2-2.5 cm in diameter, comparatively brownish-orange in the center with greenish peripheral tepals (varying to a purplish-brownish-red); fruits, firm and leathery, not juicy, yellow when ripe. Flowers in July.
Similar Species: Opuntia davisii is lower growing, has softer stems, yellow spine heaths, tuberous roots, and green sterile flowers. Opuntia whipplei is typically lower growing, joints are rigidly attached, spine sheaths vary but are most often yellow or white and flowers are yellow to yellow-green. Opuntia imbricata is larger, stems are thicker, joints are rigidly attached and flowers are flowers are normally lavender-pink to rich magenta (rarely white).
Distribution: NewMexico, Santa Fe County. The Santa Fe cholla is known from only two areas, in Santa Fe and Pojoaque, New Mexico.
Remarks: Despite this plant's name, the flowers are not very green. It is often held that O. viridiflora is a hybrid derived from O. imbricata ´ O. whipplei. All plants produce full crops of fertile seed which when germinated show individual variation, never toward any supposed parent, but rather well within the norm for O. viridiflora. Grossly similar plants of O. imbricata ´ O. whipplei hybrid origin are known from areas where the species are sympatric, such as La Plata, CO; Thoreau, NM; and the Petrified Forest National Monument, Arizona.
Conservation Considerations: Populations of this species are impacted by urban development and human activity. As with other opuntias, this species is subject to a fungal disease believed to be Gleosporium lunatum. Opuntia viridiflora is a popular "cold hardy" landscape cactus due to small shrubby habit, and its orangish flowers. It is easily propagated vegetatively and by seed, and collecting seems to offer no threat. The use of this plant as an ornamental may help with the survival and possible recovery of the species should it become extinct in its natural habitat.