Opuntia Species, Prickly Pear Cactus

The main species and all 3 varieties are indigenous to the Galapagos Islands. They eventually form good sized trunks to over 3 feet thick...Read More, and grow up to 20 feet high. Flowers on all are Yellow occasionally with a reddish hint.
The 'megasperma' variety is a Very large plant in relation to the other varieties. Flowers are over 4 inches across, and seeds up to a half inch long. Grows at sea level.
The 'mesophytica' variety has smaller seeds than 'megasperma' and flowers up to 2½ inches across. The crown is not as dense as the 'orientalis' variety.
The 'orientalis' variety's crown is very dense, flowers average 3 inches across, seeds are smaller than 'megasperma', and grows at sea level.

This is one of several species of prickly pear indigenous to the Galapagos Islands. Actually looks just like our local prickly pear here...Read More in Southern California... photo included is in a botanical garden in Santa Barbara, so not sure what it's mature size is.