IOS International Organization for Succulent Plant Study
Succulents are a diverse group of plants, variously adapted by means of storage tissue in their leaves, stems and/or roots to withstand seasonal drought and other adverse conditions. Succulence has evolved independently in numerous plant families, some that are closely related but many that are not. Though many have very attractive flowers, the common asset that is the source of their appeal as ornamentals is the enormous diversity of habits and stem-shapes displayed by such groups as the cacti and succulent euphorbias, for instance, and by the leaf-form and colour in others like the haworthias, aloes and echeverias.