(L Benson) BD Parfitt & Pinkava, Madrono 35(4): 348, 1988 
Read the Original Citation of O. engelmannii flavispina
What is Opuntia flavispina?
Opuntia flavispina is an attractive prickly pear that has long yellow spines sweeping down from the areoles. It is medium-sized, not as tall as O. engelmannii but taller than O. phaeacantha.
Plants may be approximately 1 m across and 0.5-1 m tall. The branches are ascending or prostrate with some upright branches. The obovate or oval cladodes may be 15-22 cm long and 10-20 cm wide. Primary spines are up to 7.5 cm long but are often 3 to 4 cm long. O. flavispina is characterized by a single, deflexed, long, yellow spine at many areoles. This major spine often has a burgundy base that darkens as the pads age. A much shorter secondary spine may be present. The second spine often deflexes downward more strongly than the first spine. Overall, because of the copious yellow spines, the plant often has a greenish-yellow look.
Flowers are yellow with green stigmas. Deep red fruit is roundish or barrel-shaped with a distinctly depressed umbilicus. Sometimes fruit may be longish, almost clavate. Over time the fruit becomes dull purple.
O. flavispina is hexaploid.
O. flavispina was published as a variety of O. engelmannii. Prior to that, it was described as a variety of O. phaeacantha. Nonetheless, we accept it as an undescribed, stand-alone species.
O. flavispina occurs sporadically in southern Arizona and adjacent Mexico.