Salm-Dyck, Cacteae in Horto Dyckensi Cultae Anno 1849 236, 1850
Holotype; Lectotype (deposited as O. macrorhiza pottsii); Herbarium ; Herbarium(deposited as O. macrorhiza ); Herbarium (deposited as O. compressa); Herbarium; Herbarium; Herbarium (deposited as O. macrorhiza); Herbarium (deposited as O. macrorhiza)
Opuntia pottsii is a small Opuntia, sometimes just a few inches tall. The Flora of North America (FNA) reports that there are (0)1 to 6 spines per areole, usually in the distal 40% of stem segments (or less). Spines are gray-white to red-brown or rarely yellow, erect or reflexed, terete or proximal ones flattened, sometimes spirally twisted. Spines are slender and the longest may be over 2-inches long. The FNA also reports that cladodes are not easily detached, dark green, cuneate-obovate to commonly rhombic, 2- to 8-inches long and 2- to 3(4)-inches wide. The cladodes are fleshy but firm. The plants can be confused with other small opuntias including O. polyacantha and O. macrorhiza if they are only casually observed or if they are growing among grasses, etc. However, O. pottsii is noticed in flower because it has pink, red, orange, or salmon flowers (some plants in New Mexico have yellow flowers). Britton and Rose reported that the type locality for O. pottsii is near Chihuahua, MX. See the original description. Opuntia pottsii is tetraploid.
Some O. pottsii plants grow upright from a single central stem; the pads do not crawl along the soil as is often the case with many small Opuntia species. However, other forms are prostrate and resemble O. macrorhiza. Benson (Cacti of United States and Canada, 1983) proposed a very broad concept of O. macrorhiza that included O. pottsii as a distinct variety of that species. In fact. while O. pottsii is variable, it clearly differs from O. macrorhiza by the flower color as well as the long pericarpels. There is enough variation within the species that varieties might be described, but these have not been formally published. A distribution map is provided by the Flora of North America online, but the map is conservative because the plant has been observed in more northerly and more easterly areas by the authors. In fact, O. pottsii occurs in northwestern AZ.