Prunus is a genus of trees and shrubs, including the plums, cherries, peaches, apricots and almonds. It is traditionally placed within the rose family Rosaceae as a subfamily, the Prunoideae (or Amygdaloideae), but sometimes placed in its own family, the Prunaceae (or Amygdalaceae). There are around 430 species spread throughout the northern temperate regions of the globe.
The flowers are usually white to pink, with five petals and five sepals. They are borne singly, or in umbels of two to six or sometimes more on racemes. The fruit is a drupe (a "prune") with a relatively large hard coated seed (a "stone"). Leaves are simple and usually lanceolate, unlobed and toothed along the margin.
Many species produce hydrogen cyanide, usually in their leaves and seeds. This gives a characteristic taste in small (trace) quantities, and becomes bitter in larger quantities.
The Online Etymological Dictionary presents the customary derivations of plum and prune from Latin prūnum, the plum, which is frequent in a number of authors, including Pliny. The word is not native Latin, but is a loan from Greek προῦνον (prounon) which is a variant of προῦμνον (proumnon), origin unknown. Most dictionaries follow Hoffman, Etymologisches Wörterbuch des Grieschischen, in making it a loan from a pre-Greek language of Asia Minor, related to Phrygian.
The first use of Prunus as a genus name belongs to Linnaeus in Hortus Cliffortianus of 1737, which went on to become Species Plantarum. In that work Linnaeus attributes the word to "Varr.", who it is assumed must be Marcus Terentius Varro.
In 1737 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 it clearer that all the species are more closely related. Liberty Hyde Bailey says:
Historical treatments break the genus up into several different genera, but this segregation is not currently widely recognised other than at the subgeneric rank. ITIS recognises just the single genus Prunus, with an open list of species, all of which are shown below, under "Species".
One standard contemporaneous treatment of 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 contemporaneous subgenera are described as follows:
Another recent DNA study found that Amygdaloideae can be divided into two clades: Prunus-Maddenia, with Maddenia basal within Prunus, and Exochorda-Oemleria-Prinsepia. Prunus can be divided into two clades: Amygdalus-Prunus and Cerasus-Laurocerasus-Padus. Yet another study adds Empectocladus as a subgenus to the former.
The genus Prunus includes the almond, apricot, cherry, peach and plum, all of which have cultivars developed for commercial fruit and "nut" production. The edible part of the almond is the seed; the almond seed is a drupe and not a true "nut".
There are also a number of species, hybrids, and cultivars grown as ornamental plants, usually for their profusion of flowers, sometimes for ornamental foliage and shape, occasionally for their bark. These ornamentals include the group that may be collectively called flowering cherries (including sakura, the Japanese flowering cherries).
Other species such as blackthorn are grown for hedging, game cover, and other utilitarian purposes.
Many species produce an aromatic resin from wounds in the trunk; this is sometimes used medicinally. There are other minor uses, including dye production.
Pygeum is a herbal remedy containing extracts from the bark of Prunus africana. It is used as to alleviate some of the discomfort caused by inflammation in patients suffering from benign prostatic hyperplasia.
Because of their considerable value as both food and ornamental plants, many Prunus species have been introduced to parts of the world to which they are not native, some becoming naturalised.
The Princeton finds are among a large number of Angiosperm fossils from the Okanagan Highlands dating to the late early and middle Eocene. Crataegus is found at three locations: Mcabee, Republic and Princeton, while Prunus is found at those locations and Quilchena and Chuchua. A recent recapitulation of research on the topic reports that the Rosaceae were more diverse at higher altitudes. The Okanagan formations date to as early as 52 mya, but the 44.3 mya data, which is approximate, depending on assumptions, might still apply. The authors assert: "... the McAbee flora records a diverse early middle Eocene angiosperm-dominated forest.