An orange—specifically, the sweet orange—is the citrus Citrus × sinensis (Citrus Sinensis (L.) Osbeck) and its fruit. It is the most commonly grown tree fruit in the world.
The orange is a hybrid of ancient cultivated origin, possibly between pomelo (Citrus maxima) and mandarin (Citrus reticulata). It is an evergreen flowering tree generally growing to 9–10 m in height (although very old specimens have reached 15 m). The leaves are arranged alternately, are ovate in shape with crenulate margins and are 4–10 cm long. The orange fruit is a hesperidium, a type of berry.
Orange trees are widely cultivated in tropical and subtropical climates for the sweet fruit, which is peeled or cut (to avoid the bitter rind) and eaten whole, or processed to extract orange juice, and also for the fragrant peel. In 2008, 68.5 million tons of oranges were grown worldwide, primarily in Brazil and the US states California and Florida.
Oranges probably originated in Southeast Asia and were cultivated in China by 2500 BC. The fruit of Citrus sinensis is called sweet orange to distinguish it from Citrus aurantium, the bitter orange. The name is thought to derive ultimately from the Sanskrit for the orange tree, with its final form developing after passing through numerous intermediate languages.
In a number of languages, it is known as a "Chinese apple", e.g., Dutch sinaasappel ("China's apple") or appelsien, or northern German Apfelsine. In English, however, "Chinese apple" generally refers to the pomegranate.
Oranges thrive best where the trees are chilled somewhat by occasional light frosts in winter. The trees are semidormant at that season, and temperatures just below freezing will not harm trees or fruit unless frost occurs early, before the trees have finished their annual growth. In the coldest cultivation areas, the orchards may be heated with smudge pots or smokeless natural-gas burners.
The orange thrives in a wide range of soil conditions, from extremely sandy soils to rather heavy clay loams; it grows especially well in intermediate types of soil. Orange orchards are generally planted in relatively deep soil where drainage is good. The orange trees are usually budded on stocks grown from the seed of selected trees. The seeds are sown in well-prepared soil in a lath house; after about 12 months’ growth there, the seedlings are removed to a nursery. After about 12–16 months in the nursery, the trees are usually large enough to bud. When the budded tops are one to two years old, the trees are large enough to plant in the orchard.
The culture of intercrops such as beans, tomatoes, or melons among immature orange trees is common. The growth of cover crops makes use of seasonal rainfall for production of organic matter to be incorporated into the soil. In many areas where oranges are grown, it is necessary to supplement the rainfall with irrigation; this is generally the practice in Texas, California, Israel, Spain, Morocco, and parts of South Africa. Orange trees bear abundantly from 50 to 80 years or even more, and some old orange trees whose age must be reckoned by centuries still produce crops. Oranges are picked when fully ripe, for, unlike some deciduous fruits, they do not ripen or improve in quality after being picked.
The sweet and mandarin oranges are the principal species produced commercially in the following countries, listed in order of importance: Brazil, the United States, China, Spain, Mexico, Italy, India, and Egypt. The chief orange-growing states in the United States are Florida, California, Texas, and Arizona, in that order. The world production of all kinds of oranges is approximately 70,000,000 metric tons annually.
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