Griffiths, Proceedings of the Biological Society of Washington 27(6): 27, 1914
What is Opuntia rugosa?
Opuntia rugosa is an uncommonly found prickly pear cactus that was reported from Pomona, California in the early 1900s and apparently never studied again.
O. rugosa is a low, semi-ascending, and spreading cactus to about 25 to 30 cm tall. It is 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 from a distance. The spines are white or yellowish but may darken towards the base. Areoles may have 1 to 3 centrals up to 4 to 5 cm long. Shorter subsidiary spines may be recurved. The areoles are raised and give the pads a bumpy (rugose) look.
The flowers are white with green or light green stigmas. The fruits are a little large for the size of the plant and the fruit is dark red-purple when ripe.
Ploidy is unknown.
Grown alongside other California Opuntia species, the plants are distinct. The authors have observed this species limited numbers in the immediate area of Pomona, CA near the Puddingstone Reservoir from where it was originally described. Perhaps most of its range is covered in houses now because adjacent parts of California have been heavily developed. Status reports and population studies may be warranted for this Opuntia, and it is possible the species is essentially extinct. The population observed at Puddingstone Reservoir was encountered in 1979 and observed over the years. However, plants were not observed during the last visit in 2008.
Its existence may be unknown to many California botanists because they may consider it to be the same as O. littoralis, O. vaseyi, O. semispinosa, O. phaeacantha, or even a hybrid (due to L Benson’s treatment in The Cacti of the United States and Canada, 1983). Or it may be unknown simmply because it is seldom encountered. Regrettably, Benson treated many California opuntias as hybrids. Remarkably, he proposed that many populations of cacti were actually hybrids with O. ficus-indica as one parent, a proposal that is not supported.