Griffiths, Annual Report of the Missouri Botanical Garden 20: 93, 1909
Holotype; Drawing (watercolor over photograph, Krieger and Griffith, 1915, Smithsonian Institution Archive); Photograph (D Griffiths, ca. 1910); Photograph (D Griffiths, ca. 1910); Photograph (Annual Report of the Missouri Botanical Garden, 20: 1909)
Opuntia arizonica is a seldom-reported species. It is not rare but is usually lumped into O. engelmannii. It has been found near Congress, AZ and in Tucson, AZ but probably ranges wider. Plants resemble O. engelmannii but are spinier, and O. arizonica is decidedly smaller than the large O. engelmannii. O. arizonica may be prostrate or may reach 2- to 3-ft tall or a bit more. Areoles become relatively large (nearly 3/8 or 1/2 inch) with age and dark. There are (2)3- to 4(6) stout spines per areole; the longest may be 1.5- to 2-inches long. Glochids may be scattered throughout the areoles, but are most numerous in the upper portion. The fruit is reported to be subglobose, but we have observed egg-shaped fruit. O. arizonica may be the same taxon as Opuntia sp nova aff engelmannii. See the original citation. Ploidy is not known.