Prunus

Prunus is a genus of trees and shrubs, which includes the fruits plums, cherries, peaches, nectarines, apricots, and almonds. Native to the northern temperate regions, 430 different species are classified under Prunus. Many members of the genus are widely cultivated for their fruit and for decorative purposes. Prunus fruit are defined as drupes, or stone fruits, because the fleshy mesocarp surrounding the endocarp (pit or stone) is edible. Most Prunus fruit and seeds are commonly used in processing, such as jam production, canning, drying, or roasting. Members of the genus can be deciduous or evergreen. A few species have spiny stems. The leaves are simple, alternate, usually lanceolate, unlobed, and often with nectaries on the leaf stalk. The flowers are usually white to pink, sometimes red, with five petals and five sepals. Numerous stamens are present. Flowers are borne singly, or in umbels of two to six or sometimes more on racemes. The fruit is a fleshy drupe (a 'prune') with a single relatively large, hard-coated seed (a 'stone'). Within the rose family Rosaceae, it was traditionally placed as a subfamily, the Amygdaloideae (incorrectly 'Prunoideae'), but was sometimes placed in its own family, the Prunaceae (or Amygdalaceae). More recently, Prunus is thought to have evolved from within a much larger clade now called subfamily Amygdaloideae (incorrectly 'Spiraeoideae'). In 1737, Carl Linnaeus used four genera to include the species of modern Prunus—Amygdalus, Cerasus, Prunus and Padus—but simplified it to Amygdalus and Prunus in 1758. Since then, the various genera of Linnaeus and others have become subgenera and sections, as all the species clearly are more closely related. Liberty Hyde Bailey says: 'The numerous forms grade into each other so imperceptibly and inextricably that the genus cannot be readily broken up into species.' A recent DNA study of 48 species concluded that Prunus is monophyletic and is descended from some Eurasian ancestor. Historical treatments break the genus into several different genera, but this segregation is not currently widely recognised other than at the subgeneric rank. The ITIS recognises just the single genus Prunus, with an open list of species, all of which are given at List of Prunus species. One standard modern treatment of the subgenera derives from the work of Alfred Rehder in 1940. Rehder hypothesized five subgenera: Amygdalus, Prunus, Cerasus, Padus, and Laurocerasus. To them C. Ingram added Lithocerasus. The six subgenera are described as follows: