The orange (specifically, the sweet orange) is the fruit of the citrus species Citrus × sinensis in the family Rutaceae. Probably originating in Southeast Asia, oranges were cultivated in China as far back as 2500 BC. Orange trees have been the most cultivated fruit tree in the world since 1987. Sweet oranges currently account for approximately 70% of citrus production. Over 68.3 million metric tons of oranges are grown worldwide.
All citrus trees belong to the single genus Citrus and remain almost entirely interfertile (readily and easily pollinate each other). This means that there is only one superspecies that includes grapefruits, lemons, limes, oranges, and various other types and hybrids. Interbreeding of oranges and other citrus has produced numerous hybrids, bud unions, and cultivars, their taxonomy is fairly controversial, confusing and inconsistent.
Oranges, like most citrus fruits, are a good source of vitamin C.