These appear in early spring and produce dry, single-winged fruits called samaras. The finely toothed leaves are opposite on the stems and are compound, bearing an odd number of leaflets. In North America, ashes have been subject for several years to a disease that usually kills a stricken tree in 10 years. No preventative has yet been found for the disease, which may possibly be caused by a leafhopper-borne mycoplasma. True mahoganies are members of the American genus Swietenia and the African genus Khaya.
Mahogany wood is heavy, strong, and easily worked and resists rot and termites.
It is used in cabinetry and veneers and formerly, before all the large trees were cut, in construction. Other genera in the family besides the true mahoganies also yield useful wood, oils, insecticides, and edible fruits. The chinaberry tree, Melia azedarach, native to the Himalaya, is widely planted in the southern United States as an ornamental. The family, which contains about 15 species placed in 2 genera, occurs in the North Temperate Zone. The fruits are leathery, three-valved capsules containing large, brown seeds.