AILANTHUS  

The ailanthus is a handsome tree of southeastern Asia and northern Australia. It has been naturalized in temperate climates, where it is valued as a shade tree in cities and parks for its high tolerance of air pollution. Because its seeds sprout rapidly in hot weather and cut-back trees may form thickets hard to destroy even with herbicides, the tree can be a pest. Male flowers have an unpleasant odor. The ailanthus has spreading limbs and can grow as high as 20 m (65 ft) or more--hence its name, a Moluccan word meaning "tree of heaven." The leaves, up to 1 m (3 ft) long, are composed of from 11 to 35 oval, pointed leaflets with glands on the largest notches of their margins. The small, greenish flowers grow in clusters on upper branches. In autumn the female flowers ripen into reddish-orange samara (winged fruit) that drop to the ground and are spread by winds. Ailanthus is a genus of the quassia family, Simaroubaceae. The most common species is A. altissima.