Engelmann, Proceedings of the American Academy of Arts and Sciences 3: 292, 1856 
Opuntia macrocentra has been confused with O. chlorotica santa-rita and O. azurea, but the three taxa are distinct. It is unfortunate that O. macrocentra was sometimes mislabeled as a variety of O. violaceae because that is a nonexistent species. O. macrocentra my be 2- to 3-ft tall and has circular cladodes. The spines are black. Britton and Rose reported that specimens with bluish pads can be especially showy; also see the original description. O. macrocentra may be tetraploid or diploid.
Possibly the different ploidies indicate that two different taxa exist. O. macrocentra minor has been described, but the existence of this taxon has been questioned (Powell and Weedin).
Opuntia macrocentra is a much-grown and much-enjoyed plant found in western gardens. The plants typically have long dark spines at the ends of cladodes and less often on the sides. Areoles may have 1-3 spines; pads are green, blue-green, or bluish. Many specimens turn purple or magenta in cold weather or in drought, making the plant attractive and conspicuous in a garden. Flowers are large and good looking, typically rich yellow with red centers. The red center may be a blush of red or a rich strong red collar at the base of the innermost tepals. Several branches may grow from a central stem and plants may reach 3-ft tall.