Citrus trees (genus Citrus) are tropical plants native to Southeast Asia, which appeared and diversified in the late Miocene (between 6 and 8 million years ago).

Their domestication in China and India dates back 3'000 years.
Kumquat ('Ku'), grapefruit and yuzu ('Yu') are the first species cultivated in China at that time. Poncirus ('Chih') is mentioned as a wild species around 250 BC by the poet Sung Yu. By multiple hybridizations will emerge in China the bitter oranges and mandarins (approx. 100 AD).

The lemon ('Jambira') is known in India since 800 BC.
Adopted and transmitted by the Assyrians, the Persians and then the Greeks (Theophrastus, approx. 300 BC), lemons were cultivated in Rome before the beginning of our era (Virgil, approx. 50 BC). For the Jews, the lemon was a religious symbol (Flavius Joseph, 100 A.D.), probably connected with the exile in Babylon.

Cultivated species were exchanged between China and India, as attested around 1000 AD by medical dictionaries and treatises on cultivation, produced on both sides of the Himalayas.

In Japan, the very first literary texts (around 700 AD) mention mandarins and bitter oranges. The most popular fruit in Japan today, the satsuma mandarin, was only introduced from China around 1500 AD.

Between 900 and 1200 AD, numerous Arabic treatises describe the cultivation in Spain of bitter oranges ('Naranji'), grapefruits ('Zamboa') and lemons ('Limuna'). They reveal sophisticated techniques for cultivation, preservation of the fruit and even the production of essential oils from the peel.

The crusades in Palestine contributed to the wider introduction of citrus fruits in Europe in the Middle Ages. The first mention of sweet oranges in Sicily dates back to about 1160 (Hugo Falcando). Around 1300 Piero de Crescenzi recommended "closed places" to protect the citrus fruits, already widespread in all of southern Italy.

During the Renaissance in Tuscany, the harsh winters made it necessary to cultivate in greenhouses, which the nobles would later have built as far away as Germany, France and Holland. The Italian perfumers took hold of citrus fruits, flowers or zests, in particular the Calabrian bergamot, at the origin of cologne.

In 1520, the "Chinese" orange, a common sweet orange, was cultivated in Lisbon and in the Tagus valley (Valmont de Bomare), exported to Spain, then to Europe around 1610.

The introduction on the American continent begins very early after the Spanish and Portuguese conquest. Citrus fruits find a favorable climate in the West Indies and Mexico, the quality of lemons, sweet and bitter oranges is considered better than in Europe (Gonzalo d'Oviedo 1526).

The Spanish introduced grapefruits to Florida in the 18th century. This region will be the origin of most modern commercial varieties.

From 1700 to 1800, the Italian and French Riviera was the main production center in Europe, even though lemons sometimes suffered from frost in exposed areas (1763, 1782, 1799). The trade becomes important towards all northern Europe, very organized and regulated. Volumes increased with the multiplication of plantations in Sicily (22,000 tons in 1850, 78,000 tons in 1869). Exports reach Russia and the United States.

With the beginning of industrialization, jams and essential oils became more important in Calabria and Sicily.

In Spain, large-scale plantations extended from 3,000 hectares in 1873 to 40,000 hectares in 1908, mainly of oranges. New varieties are marketed, Sicilian mandarins, Algerian clementines, American grapefruits. Hybrids are created for their fruit and their usefulness as rootstocks.

Today, citrus fruits are found on all continents. Thanks to their exceptional faculties of adaptation and hybridization, the fruits of the Citrus genus are the most cultivated in the world. The sweet orange, available in many varieties and cultivars, is the dominant fruit, with 70 million tons produced in 2000.

Freely adapted from :

The Genus Citrus. Chapter 1. Francesco Calabrese. 2002