Genus of about 1300 species and numerous cultivars of annuals, herbaceus perennials, shrubs and climbers, including some succulents and epiphytes. The estimated number of Begonia hybrids is between 1000 and 2000. Botanically there are three basic groups, depending on the nature of the underground portion. The Rhisomatous group bear thickened underground stems which are used for propagation - the members of this group are generally grown for their attractive foliage and Begonia Rex belongs here.