ailanthus, any tree of the genus Ailanthus, native to the warm regions of Asia and Australia. Ailanthus wood is sometimes used for cabinetmaking and for the manufacture of charcoal. The leaves are a source of food for silkworms, and the bark and leaves are used medicinally. Females of a species called tree of heaven, native to China, are widely grown in European and American cities because of their attractive foliage and their resistance to smoke and soot; the male flowers, however, have a disagreeable odor. Ailanthus is classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Simaroubaceae.