Citrus

First cultivated in India (the word "orange" comes from Hindi), China and Japan. With the exception of the grapefruit and other recent hybrids, the members of the citrus family are native to Southeast Asia. The citron, now known only in candied form, was brought back to Europe by Alexander the Great in the 3rd century BC, but it wasn't until the Middle Ages that the lemon and, in the 15th century, the orange, made it to the West, where they were initially treated as ornamentals and spice plants. The seedless navel orange was known along the Mediterranean by the 17th century, and the loose-skinned mandarin or tangerine species had been long cultivated in China and Japan before Europeans found them in the 19th century. The grapefruit was born in the West Indies in the 18th century as a cross between the orange and the pomelo, a large citrus fruit that had been brought to the New World a few decades earlier. The Ruby variety, with its bright red flesh, was discovered as a chance "bud sport", or mutation, on a Texas farm in 1929.

The original lime, variously called West Indian, Mexican and Key, was displaced in the U.S. by the Persian or Tahitian lime, apparently a hybrid of the lime and the citron, about 1920. The Key lime still predominates in the rest of the world. While the lemon-shaped Persian lime bears larger fruit and is more resistant to cold and pests, it's said that the small, round Key lime is more flavorful. Other notable citrus hybrids are the temple orange, a cross between mandarin and orange, and the tangelo, a mandarin crossed with grapefruit.

Citrus fruits are, of course, valued for their vitamin C content. This vitamin is more highly concentrated in the peel and pith (the white layer just under the peel) than in the flesh. The juice of an orange contains only a quarter of the vitamin C in the whole fruit, and grapefruit juice holds an even smaller proportion.

Citrus trees planted from seed take about 15 years before they bear much fruit, and they're thorny. Budded trees have practically no thorns and start bearing fruit after five years. Most Florida orange trees have lemon-tree roots. Almost all California lemon trees have orange-tree roots. One citrus tree, in fact, can, with a botanist's help, have lemons, limes, oranges, tangerines, kumquats and grapefruit growing on its branches at the same time.

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