Griffiths, Bulletin of the Torrey Botanical Club 43: 86, 1916
Opuntia zuniensis has been lumped together with O. phaeacantha, O. tortispina, or O. camanchica. Herein, it is considered to be a stand-alone taxon. The species has distinctive spination and occurs in Arizona, New Mexico, southern Utah, and perhaps southwestern Colorado. The branches of O. zuniensis are prostrate on plants that may be 10- to 12-inches tall and up to 3-ft across. Cladodes recline on their edges. Sometimes, a pad will rise above the others. Cladodes are obovate, oval, or rhomboid and may be acute at both ends. Mature cladodes may reach 4(5)-inches across and be 6(10)-inches long. Areoles are often a half-inch apart or a bit more on mature cladodes. Spines are white(ish) but can be straw-yellow on the apex of new growth. There are up to 6 spines at the apex of new growth, and one or more may be 2 inches long. Over time the apex spines may reach 3 inches in length. Read the original description.
O. zuniensis is usually found growing on sandy soils of grasslands or pinon-juniper woodlands; sometimes it is found in the in Navajoan Desert. If it is growing on slopes or in rocky areas, it will usually grow in pockets of sandy soil.
O. zuniensis is a monotypic species; it is not as variable as other Opuntia of similar size. Rarely, the flowers of O. zuniensis are light orange instead of light yellow. Also uncommonly, the bases of the white spines may darken slightly. Overall, O. zuniensis has a shaggy look due to its spines. O. zuniensis often blooms 2- to 3-weeks later than O. polyacantha.