Griffiths, Annual Report of the Missouri Botanical Garden 21: 169, 1910
Drawing (Britton and Rose, v1 1919, fig 174)
Opuntia lubrica is a spineless plant that has some similarity to O. rufida; however, O. lubrica has shiny pads that are not pubescent. Some plants are strongly purplish in AZ, especially when they are stressed or dormant. The plant may reach 18-inches tall and has a habit similar to that of O. microdasys, but overall it is a more robust plant. O. lubrica my make a low shrub to over 3-ft wide. Cladodes of the current year may be nearly circular or obovate and 6- to 7- inches wide by 8- or 9-inches long. O. lubrica has tight, dense clumps of prominent but short glochids, yellow to dark rust red; they increase in number and length on older stems. Sometimes a few insubstantial spines (same color as the glochids) form, but usually the plants are spineless. Britton and Rose reported that, at the time, the species was known only from the type locality in Mexico. See the original citation.
In the US, Opuntia lubrica grows in far southern AZ where it often prefers rocky walls of canyons. The flowers are bright yellow, often a little greenish in the center, sometimes developing a brassy or slightly orange hue as they age. Fruit is greenish to more often bright red, juicy, and with lots of areoles and short glochids (much like those of O. rufida and O. microdasys, but larger).
Dave Ferguson reports:
O. lubrica may have hybrid origins, and possibly the plants in Arizona are not related to the ones in eastern Mexico. However, they all look related to one another. It is possible (but not at all demonstrated) that the plants in San Luis Potosi may be derived from O. cacanapa x O. microdasys. In Coahuila they might be derived from O. cacanapa x O. rufida. In Arizona they might be O. chlorotica var. santa-rita x O. microdasys. These suppositions are not demonstrated and perhaps all 3 populations constitute a single species with a common origin and different origin.
In Mexico I have mostly seen the plants on rocky slopes east of, or in the eastern part of, the Chihuahuan Desert, usually not in stark desert conditions (in the same areas that O. cacanapa favors). In Mexico, I’ve never seen a plant with purplish coloring (other than a tiny hint around the areoles when it gets really cold, and only in some plants). O. lubrica grows from at least as far north as the Monclova area and the Sierra de la Paila in Coahuila south into San Luis Potosi. There are never large colonies, just scattered individuals.