Ailantus (Malay, ailanto, tree of heaven, the name of one species in the Moluccas), a tree of the sub-family ailanteae, which is one of the four divisions of simarubaceae of Lindley. The species A. glandulosa, native of China, was introduced into England in 1751, and into North America about the beginning of this century. The tree resembles a gigantic stag's horn sumach, with very large leaves, unequally pinnate, and footstalks from one to two feet in length. It has many flowers on a terminal pedicel, whose anthers smell disagreeably, like animal effluvia containing phosphorus. It grows very fast, especially in poor calcareous soil, and has spreading roots. There is a resinous juice in the bark, which hardens in a short time. The wood is hard, heavy, glossy, and susceptible of a fine polish. It is propagated by root-cuttings. It sometimes has only male flowers, but in warm countries produces both male and female, and consequently fruit. A. excelsa is found about Delhi and further south. There are other species in southern Asia, and on the islands of the Indian ocean.

The other plants of the same order are natives of tropical America, India, and Africa.