Opuntiamojavensis is an enigmatic prickly pear cactus. The only historical drawing of this cactus shows 2 spine clusters and an immature or sterile fruit. The lectotype for this prickly pear also has limited material. It is found at elevation at the summit of Mt. Potosi in southern Nevada and in similar places westward.
O.mojavensis forms woody-stiff plants sprawling to 2 m across. O.mojavensis has distinctly angular branches caused by its woody nature as well as sometimes-rising branches. Cladodes are irregular in size but often obovate. The spines seem similar to those of the lectotype as well as in the drawing above. However, spination is irregular and there are 0-2(5) spines per areole, even on the same pad. Plants may turn a pleasing red-purple color in winter.
Flowers are 5-8 cm across and yellow with distinct or light red centers, green stigmas, and yellow anthers. Outer tepals may be tinged with red or red-orange. Fruit is reddish and may be barrel-shaped.
Ploidy is unknown.
We observed a population of plants growing at the summit of Mt Potosi (Highway 160 summit) near Las Vegas, Nevada that we interpret be O.mojavensis. We base our description of the taxon on that population and on similar plants found further west mostly in the trans-montane regions of California. The original location (mountains above Victorville/Hesperia, California) matches the Mt Potosi location in general terms of plant companions and altitude but is about 150 miles west of Mt. Potosi. Thus, we envision O.mojavensis as a species of high elevations west of Arizona and across the Mojave Desert into the mountains of southern California. Though it is obviously a desert plant, we have seen the taxon at Big Bear Lake in California.
Because of its attractive flowers, angular growth shape, and obvious cold hardiness, O.mojavensis would be interesting in a garden. However, it is a large sprawling plant.