Opuntia macrorhiza Opuntia macrorhiza Opuntia macrorhiza is a common and widespread species of cactus with the common names plains prickly pear or twistspine pricklypear or Western pricklypear. It is found throughout the Great Plains of the United States, from Texas to Minnesota, as well as in the desert and Rocky Mountain states from Arizona to Idaho, with sporadic populations in the Mississippi and Ohio Valleys. It is also reported from northern Mexico, in the states of Chihuahua, Sonora, Coahuila, Nuevo León, Durango, Tamaulipas, and San Luís Potosí. The species is cultivated as an ornamental in other locations. The species prefers dry, sandy
Opuntia readily between species. This can make classification difficult, yielding a reticulate phylogeny where different species come together in hybridization. Also, not all species listed here may actually belong in this genus, meaning that "Opuntia" is not a monophyletic group. "Opuntia" also has a tendency for polyploidy. The ancestral diploid state was 2n=22, but many species are hexaploid (6n = 66) or octaploid (8n = 88). Chollas, now recognized to belong to the distinct genus "Cylindropuntia", are distinguished by having cylindrical, rather than flattened, stem segments with large barbed spines. The stem joints of several species, notably the jumping cholla ("Cylindropuntia