Although native only to the Northern Hemisphere, plum trees (Prunus spp.) today are grown worldwide in temperate climate areas with cool to cold winters. Only Antarctica lacks any gardens with ornamental or fruiting plum trees. Numerous hybrids of European, eastern Asia and North American plum species exist today.
Classification and Origins
Plums are members of the the rose family, Rosaceae, and are grouped in the subfamily Amygdaloideae, making them close relatives of peaches and cherries. All plum species are placed in the genus Prunus. Although there are plum species native to all Northern Hemisphere continents, the plum as an important food source centered in eastern Asia, particularly China, as well as in eastern Europe. Europeans spread the plum as a commodity to other parts of the world from the 16th century onwards where necessary cool to cold winter climates favored springtime flowering.
Popular Plum Species or Types
There are two species of plums that are especially important for fruit production, European plum (Prunus domestica) and Japanese plum (Prunus salicina). Hybrids between these two species are widely grown worldwide where hardy for their different fruit qualities.
In North America, wild plum species may be seen in natural areas, especially in spring when their flowers appear before other trees break their winter dormancy. The American plum (Prunus americana) and chickasaw plum (Prunus angustifolia) are two species that produce small fruits for eating. Over 600 varieties of plums have been bred by crossing North American plum species with either the European or Japanese plum.
Not all plum trees were bred or selected for their fruits. Ornamental plums have either spectacular spring flowering displays or attractive foliage. Although all plums have ornamental qualities, those hybrids that fail to produce consistent or good-tasting fruits are usually called ornamental to distinguish them for landscape use rather than for orchards.
The United States is a top producer of plums, with the trees being raised in all states except Alaska, according to Simpson and Ogorzaly in "Economic Botany:Plants in Our World." Other top-producing nations of edible plums include China, Germany, the Balkan States and Romania.
Plum trees, both fruiting and ornamental types, are grown in countries that have cool to cold winter temperatures needed for a physiological process called vernalization. Plum trees must be exposed to varying lengths of cold in the winter to initiate the formation of flowers. If the threshold of chilling does not occur, flowering is absent or greatly reduced.
Plum trees are grown in varying degrees on all continents except Antarctica. In the Southern Hemisphere, Australia, New Zealand, South Africa, Argentina and Chile are known to grow plum varieties in gardens. In the Northern Hemisphere, plums are widespread in the United States, Canada, all of Europe eastward into China, the Korean Peninsula and Japan.