Pereskia is a cactus genus that is most unlike all other members of the family. Except for the defining characteristic of spine-bearing areoles and some floral characteristics, the plants in this genus are anything but cacti.
This is a tropical genus that grows as typical deciduous trees or shrubs that consist of a woody trunk and branches with flat leaves. Some people have insisted that it is not correct to say that "all cacti are succulents" because of the genus Pereskia, however, many have some form of root succulence or to a lesser degree in the stem and all of them produce thicker, rubbery leaves. These leaves are fleshy like that of a Portulaca and not "papery" like those in an Oak or a Maple tree.
In the wild, these plants are typically found among other trees and shrubs and their presence is not immediately apparent. In flower, the shrubs can be quite brilliant and individual flowers are reminiscent of a wild rose, hence the common name sometimes used: Rose Cactus.
Due to the large size and tropical nature of these plants, they are seldom found in cultivation. P. grandiflolia is the most common species to be found in cultivation, if anything.