Elms are deciduous and semi-deciduous trees comprising the genus Ulmus, family Ulmaceae. Elms first appeared in the Miocene period about 40 million years ago. Originating in what is now central Asia, the tree flourished and established itself over most of the Northern Hemisphere, traversing the Equator in Indonesia. During the 19th and early 20th centuries, many species and cultivars were planted as ornamentals in Europe, North America, and parts of the Southern Hemisphere, notably Australasia. Elm leaves are alternate, with simple, single- or, most commonly, doubly-serrate margins, usually asymmetric at the base and acuminate at the apex. The genus is hermaphroditic, having perfect flowers which, being wind-pollinated, are apetalous. The fruit is a round wind-dispersed samara. All species are tolerant of a wide range of soils and pH levels but, with few exceptions, demand good drainage. The other genera of the Ulmaceae are Zelkova (Zelkova) and Planera (Water Elm). Celtis (Hackberry or Nettle Tree), formerly included in the Ulmaceae, is now included in the family Cannabaceae.

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