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.