Ailanthus altissima Mill. Swingle (Tree of Heaven)

Abstract

The genus Ailanthus (family Simaroubaceae) comprises 15 species growing in east and south Asia and in north and east Australia. Ailanthus altissima Mill. Swingle (syn. A. glandulosa Desf.) is a large deciduous tree (Fig. 1) which has been cultured since 1751. It is represented by two varieties: var. erythrocarpa Rehd. with light red fruits, and var. pendulifolia Rehd. with hanging leaves. A. alitssima, also known as the tree of heaven, has been introduced into many countries, e.g., India, Japan, and northern Australia, and now is also common in the whole of Europe and America. During hard winters it is not frost-resistant, but regenerates rapidly. Plants can be cultivated either from ripe seeds or from suckers. They are characterized by the ability to produce many root suckers, and thus these plants are not suited for cultivation in small gardens. Because these plants are photophilous, they have to be cultured single in open areas. They grow quite rapidly, reaching 30 m height even on poor and sandy soils, can survive in smoky areas and are also tolerant to city pollution. The trees have gained popularity due to their compact habit, deciduous leaves, and colorful autumn fruits. Ailanthus altissima, unlike other genera belonging to the Simaroubaceae, possesses floral nectaries of a wide diversity of forms and position. The stem and leaves are covered with characteristic glandular and nonglandular hair. The lignified hair in buds protect young leaves against the cold. Since A. altissima grows preferentially in dry soil with much sun it is perhaps possible that trichomes play a role in the regulation of moisture exchange with the atmosphere. The unpleasant smell of the foliage is due to the secretory products of glandular hairs, and is repulsive to insects (Bory and Clair-Maczulajtys 1980). In the Far East, various parts of A. altissima are used for medicinal purposes, i.e., fruits or bark of root and stem are used for dysentery and intestinal disorders. The leaves are toxic to domestic animals, causing inflammation of the digestive tract. The bark contains compounds such as oleoresis, bitter and aromatic essences, some mucilage, ailanthin, calcium oxalate, and isoquercetin (Roberts 1991).