Opuntia robusta Opuntia robusta Opuntia robusta, the wheel cactus, nopal tapon, or camuesa, is a species of cactus in the Cactaceae family. It is native and endemic to central and northern Mexico to within 100 miles of the Arizona and New Mexico borders where it grow from 5,000 to 10,000 feet on rocky slopes, open shrub lands, woodlands and mixed with other cactus and succulents. Plants are commonly around high, though they may grow to over high when supported. The flattened stem segments are fleshy, round and blue-grey in colour. These are up to in diameter and have sharp spines up to
Opuntia fragilis in). Both the common and scientific names refer to the easily detached stem segments. This is known to be a means of plant dispersal. "Opuntia fragilis" is a small, prostrate plant, rarely more than 4 inches high: joints tumid, fragile, easily detached, oval, elliptical, or subglobose, 1-2 in. long and nearly as thick as broad, bright green: areoles ¼-½ in. apart, with whitish wool and a few white to yellow bristles, which are much longer and more abundant on older joints; spines 1-4, occasionally a few small additional ones, weak, dark brown, the upper one usually longer and stronger than