The genus Crassula is one of the most diverse succulent genera, varying from tiny moss-like annual plants to 2m tall succulent trees like Crassula ovata. Belonging to the Crassulaceae family, there are more than 300 Crassula species of which approx. 150 are found in southern Africa, where they are widespread but concentrated in the semi-arid winter-rainfall areas. The centre of distribution of this genus is in southern Africa, but they extend beyond Africa into Europe, America, Australia, New Zealand and the southern islands. The name Crassula is the diminutive of the Latin crassus which means thick or fat, referring to the fleshy nature of the genus as a whole. This popular genus offers an extensive array of sizes, growing forms and textures making them perfect for landscaping, rockeries, windowsill plants or to be grown in containers. They can also be grown indoors as house plants. Those that make excellent house plants are the glossy leaf varieties. Crassulas, given a rich, well-drained medium will grow fast and luxuriantly.

Crassula arborescens is another South African indigenous plant. Unlike most crassulas which are relatively small succulent plants, Crassula arborescens is an outstanding, squat, succulent tree that is easily recognizable by its unmistakable blue-grey foliage that contrasts well with the other plants on hillsides in the karroid scrub. It has a very attractive appearance in both its natural habitat and cultivated gardens. Crassula arborescens is a large and impressive looking single-stemmed, many branched shrub or small tree, easily reaching a height of up to 3 m. The trunk is thick and fleshy and has a smooth, green-grey bark. As with some other members of Crassulaceae, the tree crassula is used medicinally in the treatment of epilepsy. The roots of Crassula arborescens subsp. arborescens are edible and eaten in Swaziland where it is known as Umchobozovithi. Horticulturally the plants are very popular in rock gardens, on rocky embankments, slopes and as container or bonsai plants. Their easy cultivation has led to them being used extensively in gardens in southern Africa. Besides their attractive flower clusters, they look delightful with their contrasting blue-green foliage, especially when used in combination with other dark green shrubbery.