the elm family of the nettle order (Urticales), with 15 genera of trees and shrubs, distributed primarily throughout temperate regions. Members of the family have watery sap, and its leaves alternate along the stem. The leaves usually have toothed edges and often are lopsided at the base. The flowers lack petals. Male and female flowers are borne together or apart on the same plant. The fruit, a samara, may be winged, fleshy, or nutlike.

Elms (Ulmus) and hackberries (Celtis) are important shade and ornamental trees. The planer tree, or water elm (Planera aquatica), of southeastern North America produces useful timber known as false sandalwood. Trees and shrubs in the Eurasian genus Zelkova sometimes are planted as ornamentals. See also elm; hackberry; Zelkova.