The Ulmaceae or Elm family is a small family of flowering plants with about 9 genera and 130 species found world-wide in tropical and northern temperate regions.
The estimation above includes the genus Celtis which, after molecular phylogenetic studies, is recommended for inclusion in the Cannabaceae Family.
In North America there are about 6 genera and 58 accepted taxa overall. The largest genera include (Elms) Ulmus, (Hackberries) Celtis, Zelkova and Ampelocera. Members of Ulmaceae are trees and shrubs.
The largest genera in the Elm Family found in North America are: Celtis (20 species) Ulmus species (14) and Trema (5 species).
Although evolving under isolated conditions, Elm trees (Ulmus) exist in Europe and North America and appear to have different biological resistances.
Common characteristics: Plants: bark smooth to deeply fissured, watery sap. Leaves: evergreen; alternate, simple, stipules and petioles present, margins entire or dentate, venation pinnately veined or palmately veined. Inflorescence: axillary, cymes, racemes, fascicles or solitary. Flowers: bisexual or unisexual, flowers lack petals, staminate and pistillate on same plants sepals persistent, stamens usually as many as calyx lobes, wind pollinated. Fruit: fleshy drupes, samaras or nut-like.
Elms Trees, (Ulmus) and Hackberries, (Celtis) are useful and important for shade and as ornamental landscape trees and trees of the genus Zelkova are also used for ornamental landscape purposes. Elms are also important as timber trees used in making furniture as is the Planer Tree or Water Elm (Planera aquatic). The Slippery Elm (Ulmus rubra) has bark that can be used for medicinal purposes.