Opuntia ficus-indica system. The plant may be used as an ingredient in adobe to bind and waterproof roofs. "O. ficus-indica" (as well as other species in "Opuntia" and "Nopalea") is cultivated in nopalries to serve as a host plant for cochineal insects, which produce desirable red and purple dyes, a practice dating to the pre-Columbian era. Mucilage from prickly pear may work as a natural, non-toxic dispersant for oil spills. A commercial use for "O. ficus-indica" is for the large, sweet fruits, called tunas. Areas with significant tuna-growing cultivation include Mexico, the Mediterranean Basin, Middle East and northern Africa. The cactus grows
Opuntia engelmannii (state) to the Tamaulipan matorral in Chihuahua (state), in Mexico. In the Sonoran Desert, terminal pads face predominantly east-west, so as to maximize the absorption of solar radiation during summer rains. Although found occasionally in the Mojave Desert, it tends to be replaced by "Opuntia basilaris", which does not need the summer rain. The overall form of "Opuntia engelmannii" is generally shrubby, with dense clumps up to high, usually with no apparent trunk. The pads are green (rarely blue-green), obovate to round, about 15–30 cm long and 12–20 cm wide. The glochids are yellow initially, then brown with age. Spines