Citrus Trees - Biology Of Citrus, Cultivation And Economic Products Of Citrus Trees, The Sweet Orange, The Tangerine Or Mandarin Orange - The grapefruit, The lime

Citrus trees are various species of trees in the genus Citrus, in the rue family, or Rutaceae. There are 60 species in the genus Citrus, of which about 10 are used in agriculture. The center of origin of most species of Citrus is southern and southeastern Asia. Citrus trees are widely cultivated for their edible fruits in sub-tropical and tropical countries around the world. The sweet orange (Citrus sinensis) is the most common species of citrus in cultivation, and is one of the most successful fruits in agriculture.

The rue family consists of about 1,500 species and 150 genera. Most species in this family are trees or shrubs. The greatest richness of species occurs in the tropics and subtropics, especially in South Africa and Australia. However, a few species occur in the temperate zone. Several species native to North America are the shrubs known as prickly ash (Zanthoxylum americanum), southern prickly ash (Z. clava-herculis), and three-leaved hop tree (Ptelea trifoliata).

The grapefruit or pomelo (Citrus paradisi) is a variety of cultivated citrus tree whose geographic origin is not known, but is likely native to Southeast Asia. The fruit of the grapefruit has a yellowish rind, and is relatively large, as much as 1 lb (0.5 kg) in weight. The pulp and juice of the grapefruit are rather bitter and acidic and are often sweetened with cane sugar before being eaten.

The lime is native to Southeast Asia and is very susceptible to frost. More sour than the lemon, the lime (C. aurantifolia) cannot be eaten raw. However, the lime can be used to make a sweetened beverage known as limeade, and an extract of its juice is widely used to flavor commercially prepared soft drinks.