Oranges, lemons, limes, tangerines, kumquats and grapefruits are all citrus fruits. Citrus fruit contains large amounts of vitamin C, limonoids, and citric acid. Citric acid lends citrus fruit its characteristic sour taste.
Citrus fruit grows on trees or evergreen shrubs. While wild species of citrus trees can grow as tall as 16 meters, many farming operations have bred shorter dwarf varieties to ease the agricultural process and increase efficiency.
Citrus-producing plants prefer warm environments with abundant moisture. Therefore, most species of citrus plants originate in tropical or subtropical Asia before being spread to other areas of the world. While scientists know relatively little about the origins of citrus plants, some believe that all modern varieties have developed from cross breeding between four original species: lime, grapefruit, citron and mandarin.
A thick rind and peel with a soft and juicy interior distinguish citrus fruit from other varieties. People consume citrus fruit either by eating the inner flesh after separating it from the rind or by squeezing the fruit and consuming the juice. The kumquat is one of the only citrus fruits with an edible rind. However, the peel of lemons, limes, oranges, and grapefruit are commonly used as flavoring agents, as they contain highly aromatic oils.
As of October 2013, oranges were the highest-selling citrus fruit per capita in the United States. The grapefruit, lemon, tangerine and lime follow the orange in popularity. Domestic production of these crops followed the same pattern as consumption.