Griffiths, Proceedings of the Biological Society of Washington 27(6): 27, 1914
Opuntia rugosa was reported from Pomona, CA in the early 1900s and apparently never again. It is a low ascending and spreading plant to about 2-ft tall. It is a about the size of O. camanchica; however, it may have branches that try to grow vertically for a few years. Plants often appear yellowish-green. The spines are white or yellowish, but may darken towards the base. Areoles may have 1 to 3 centrals up to 2-inches long. Shorter subsidiary spines may be recurved. The areoles are raised and give the pads a bumpy (rugose) look. The fruits are a little large for the size of the plant and dark red-purple when ripe. Grown alongside other CA Opuntia species, the plants are distinct. This species may be limited to the immediate area of Pomona, CA near the Puddingstone Reservoir, and if so, most of its range is covered in houses now. Status reports and population studies may be warranted, and it is possible the species is essentially extinct. Its existence may not be known to many CA botanists because they may consider it to be the same as O. littoralis, O. vaseyi, O. semispinosa, O. phaeacantha, or even a hybrids due to L Benson’s treatment (The Cacti of the United States and Canada, 1982) of opuntias. See the original description.
O. rugosa is a low spreading plant about the same size as O. camanchica but more likely to have a few branches that try to grow vertically for a few years. The pads are light green and raised around the areoles (making their surfaces “rugose” or bumpy).