Taxonomy of the three arborescent crassulas, Crassula arborescens (Mill.) Willd. subsp. arborescens, C. arborescens subsp. undulatifolia Toelken, and Crassula ovata (Mill.) Druce (Crassulaceae) from southern Africa

Summary: In southern Africa, the family Crassulaceae consists predominantly of low-growing to medium-sized succulent herbs and shrubs, with only four taxa (three species and a subspecies) attaining tree-like dimensions. We discuss the taxonomy of the three tree-like taxa in the genus Crassula L. (Crassula arborescens (Mill.) Willd. subsp. arborescens, C. arborescens subsp. undulatifolia Toelken, and Crassula ovata (Mill.) Druce) that have been accorded National Tree List numbers in South Africa. The species are described, illustrated, and their geographical distribution ranges are mapped. A key to differentiate the taxa is provided.