Opuntiahybridizes readily between species. Perhaps only oaks do so as readily.[1] This can make classification difficult. Also, not all species listed here may actually belong into this genus.
Opuntia aciculata
Opuntia anacantha
Opuntia atrispina
Opuntia auberi
Opuntia aurantiaca
Opuntia basilaris– Beavertail cactus
Opuntia boldinghii
Opuntia chaffeyi
Opuntia chlorotica–Pancake Prickly Pear; native to southwest USA and the Sonoran and Mojave deserts.
Opuntia clavata
Opuntia cochenillifera
Opuntia comonduensis
Opuntia compressa
Opuntia curvospina
Opuntia decumana
Opuntia decumbens–Nopal de Culebra
Opuntia dejecta
Opuntia echios
Opuntia echios var. gigantea– Galápagos prickly pear. Galápagos Islands.
Opuntia macrocentra–Black-spine Prickly Pear, Purple Prickly Pear. Found in southwest USA and northern Mexico.
Opuntia macrorhiza–Plains Prickly Pear. Found throughout the Great Plains except for the northernmost areas (not found in North Dakota), and extending sporadically eastward as far as Kentucky. Syn. O. leptocarpa MacKensen, O. tenuispina Engelm., O. tortispina Engelm. & Bigelow
Opuntia polyacantha–Panhandle Prickly Pear. Found in the Great Plains, Great Basin, Mojave Desert, Colorado Plateau, and the Rocky Mountains. Syn. O. rhodantha K.Schum.
Opuntia polyacantha var. arenaria (syn. O. erinacea)
Opuntia pubescens (syn. O. pascoensis Britton & Rose)
Opuntia pusilla–Creeping cactus. Syn. O. drummondii Graham
Opuntia rastrera
Opuntia repens
Opuntia robusta
Opuntia rufida (sometimes included in O. microdasys)