Ash (tree)

Ash (tree), common name for any member of a genus of plants (see Olive), comprising about 70 species of mostly northern temperate trees and shrubs, valued for timber and ornament. Characteristic of the group are the small, inconspicuous greenish flowers, usually borne in clusters with or without sepals and petals. 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. The white, or American, ash, European ash, and Siebold ash of Asia are particularly valuable sources of woods used in cabinetry. The flowering, or manna, ash, notable for its long petals, is cultivated in Mediterranean regions for its sweet gum (see Manna). In North America, ashes have been subject for several years to a disease that usually kills a stricken tree in ten years. No preventative has yet been found for the disease, which may possibly be caused by a leafhopper-borne mycoplasma.

Mountain ash is an unrelated tree of a different family (see Rose). The prickly ash, also called Hercules'-club, also belongs to a different family (see Rue).

Scientific classification: Ash trees constitute the genus Fraxinus, of the family Oleaceae. The white, or American, ash is classified as Fraxinus americana, the European ash as Fraxinus excelsior, the Siebold ash as Fraxinus sieboldiana, and the flowering, or manna, ash as Fraxinus ornus. The mountain ash belongs to the family Rosaceae, and the prickly ash to the family Rutaceae.