(Engelmann & J. M. Bigelow) Britton & Rose, Smithsonian Miscellaneous Collections 50: 535, 1908
Lectotype (O. missouriensis trichophora); Lectotype (O. polyacantha trichophora); Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Drawing (The Botany of the Expedition, 1856, plate XV No. 1-4 [O. missouriensis trichophora])
Opuntia trichophora can appear similar in overall appearance to O. diploursina. Both may have spines that are very slender and flexible, forming hairs that can be over 6-inches long. Some plants may not have long hair-like spines and can have a wooly appearance with many short spines. Other plants may not have a wooly appearance and are mostly spined in a “normal” manner. The fruit has many thin, flexible spines or may have thin stiff spines. The fruits can be very spiny. O. trichophora is obviously related to O. polyacantha and O. diploursina. We follow Britton and Rose (1919) and their description of this plant as a distinct species. See the original description. O. trichophora is diploid.
Dave Ferguson writes:
Some individuals may have slender spines longer than 6 inches. Sometimes the hair-like spines are located only on the underside of the plant, are few in number, and are early deciduous. Occasionally plants have no discernible long hairs. The smallish pads are frequently obscured by the presence of many spines–up to 12 or 15 per areole, and there may be 6 or more centrals. Like O. polyacantha, the seeds are irregular in outline and large.
O. trichophora often grows on hot rocky slopes or cliff faces in mountainous or otherwise dissected terrain, but it can grow on gypsum soils or even sandy soils in grasslands or pinon-juniper woodlands. Some populations grow in baking hot conditions (e.g., on south- or southwest-facing sunny basalt cliffs). O. trichophora grows above 3000 ft and often grows at 5000 ft or higher. It has been anecdotally reported at 9000 ft.
The species occurs throughout much of Colorado Plateau and north into WY along Flaming Gorge. It may be observed east of the central mountains of UT, on the western side of CO, in northern AZ, in most of NM west of the Great Plains, in trans-Pecos TX, and into Mexico.