Oranges are citrus fruits and characterized by a thick peel and sectioned interior. Although most citrus fruits have seeds, a number of seedless varieties of oranges are available. Oranges are a hybrid, so do not grow in the wild. They are thought by some to have been a cross between a pomelo and a tangerine, but because the hybridization happened during prehistoric times, the actual origins are not known.
Oranges are generally thought to have originated in China, the Assam area of India and Burma, or elsewhere in southeast Asia in prehistoric times. Initially, only sour oranges were known in Europe until the Romans brought back living sweet orange trees by sea. European orange cultivation died out with the Roman Empire, but oranges were cultivated in North Africa. Oranges were reintroduced to Europe around the ninth century A.D.. Oranges were introduced to the Americas with seeds carried by Christopher Columbus.
There are many varieties of oranges cultivated around the world. In 1818, a booklet published by Risso and Poiteau described eight species of orange with 169 different varieties. The most common orange cultivated is the sweet orange, followed by the Bahianinha. Brazil is the world's largest orange exporter and the Bahianinha makes up 30 percent of Brazil's orange crop.
One of the most common and popular oranges in Asia is the original Chinese mandarin orange. Mandarin oranges have spread throughout the world and can usually grow in any region with a climate suitable for citrus cultivation. Mandarins are more resistant to cold than many sweet oranges, and as such do well in more northern areas.
Many people believe that a fruit-bearing tree will grow well from seed. With most sweet oranges, planting the seeds will result in a sour orange tree. Most sweet orange trees are created via grafting a sweet orange scion to a sour orange root stock.
Climate and Indoor Growing
Outdoor orange orchards require long growing seasons with long hot spells that allow the fruit to sweeten. This limits the areas where oranges will grow outdoors. However, recent developments in dwarf citrus trees allow you to grow a producing citrus tree in colder climates by bringing the tree indoors for the winter.