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)
What is Opuntia arizonica?
Opuntia arizonica is a seldom-reported species of prickly pear cactus. It is not rare but is usually lumped into O. engelmannii and thus is an unnoticed Opuntia. It has been found near Congress, AZ and in Tucson, AZ but probably ranges much wider.
This prickly pear cactus resembles O. engelmannii but is spinier. Additionally this particular Opuntia is decidedly smaller than the large O. engelmannii. O. arizonica may be nearly prostrate or may ascend to 20 cm to 30 cm tall or a bit more. Plants my be 50 cm across, or they may sprawl to 1 m. Cladodes are typically 25-30 cm across and subcircular. Areoles become relatively large (1.5-3 cm across) with age and they darken. Sometimes the tissue of an areole my proliferate creating a bump in the center. There are (2)3-4(6) stout spines per areole on this Opuntia; the longest may be 2.5 to 5 cm long. Generally spines are erect, but lower ones may recurve. Glochids may be scattered throughout the areoles, but are most numerous in the upper portion. The fruit of this prickly pear is reported to be subglobose, but we have observed egg-shaped fruit. O. arizonica may be the same taxon as O. sp nova aff engelmannii. See the original citation. Ploidy is not known.