Opuntia polyacantha
is similar to Opuntia macrorhiza.
O. polyacantha has shorter spines, and the spines are spaced closely
together. Spines are of similar length throughout the pad. For O.
macrorhiza, spines are longer, spaced farther apart, and are shorter
toward the base of the pad. Flowers of O. polyacantha range from yellow
to red, with yellow flowers being most common.
