Orange is a small evergreen tree grown in sub-tropical climates and is probably native to southeast Asia; however, it is not known in the wild form. It was probably first cultivated in China, and is now a very popular house plant, particularly when it bearsand begins to develop fruit. The fruit is a special kind of berry called a hesperidium; the outer layer of the pericarp (flavedo) is coloured orange or yellow and the inside layer (albedo) is white. In the orange, the rind adheres tightly to the pulp and is more difficult to peel than the loose-skinned mandarin orange.
In winter, the orange requires a low temperature of 5°-10°C (41°-50°F); when grown outdoors, it even tolerates a light frost. Water liberally in summer but restrict water in winter, especially if it is grown in cool conditions. It does not tolerate water containing lime. Orange may be propagated bysown in spring, or by , taken with three to five buds any time between spring and autumn. Cuttings produce results more rapidly. The best method of , however, is by grafting on to Ponci-rus trifoliata or Citrus aurantium .