Griffiths, Bulletin of the Torrey Botanical Club 43(2): 90, 1916
Opuntia pyrocarpa is a commonly encountered prickly pear cactus in central and north-central Texas where it grows in deep limestone-derived soils. The cactus may occur well into Mexico. Though we have not observed it in Oklahoma, it seems possible that this Opuntia species is there. It is an ascending spreading plant to 24-inches tall. Often the main branches of this prickly pear cactus are prostrate but ascend at the ends. The cladodes are large, approximately 25(30) to 15(20) cm, or they may be smaller in some plants. The cladodes are constricted at the base to form a short neck. The spines are porrect in new cladodes, but often slope down with age. Spines are present on the upper 50% to 60% of the areoles and are yellow darkening to a brown base. Spines are 2 to 3 cm long. The flowers are yellow with light-red centers or pure yellow. This Opuntia has a white style tipped with a light-green stigma. The fruit is long, pyriform, and various shades of carmine, often with a purplish tinge outside and inside.
O. pyrocarpa may create large plants that resemble piles of cladodes spread over 6-8 feet, making up for lack of height by achieving breadth. Several large plants growing together can create a formidable thicket. The species occurs with other species of Opuntia found in central Texas such as O. lindheimeri, O. macrorhiza, and O. orbiculata, etc. The type location is Marble Falls, TX. See the original description.