A clementine is a variety of mandarin orange (Citrus reticulata), so named in 1902. The exterior is a deep orange colour with a smooth, glossy appearance. Clementines can be separated into seven to fourteen segments. They tend to be very easy to peel, like a tangerine, but are almost always seedless. For this reason they are sometimes known as seedless tangerines; the clementine is also occasionally referred to as the Algerian tangerine. They are typically juicy and sweet, with less acid than oranges. Their oils, like other citrus fruits, contain mostly limonene as well as myrcene, linalool, α-pinene and many complex aromatics.
Most sources say that the clementine came to exist because of accidental hybridization, with the first fruits discovered by Father Clément Rodier in the garden of his orphanage in Misserghin, Algeria. However, there are claims it originated in China much earlier; one source describes it as nearly identical to the Canton mandarin widely grown in the Guangxi and Guangdong provinces in China.
The clementine is not always easy to distinguish from other varieties of mandarin oranges. As such, it should not be confused with similar fruit such as the satsuma or honey sweet orange, or other popular varieties.
This variety was introduced into California commercial agriculture in 1914, though it was grown at the Citrus Research Center (now part of the University of California, Riverside) as early as 1909. Clementines, usually grown in Algeria, Spain, Portugal, Morocco, Greece, Italy, Israel, Lebanon, and Turkey have been available in Europe for many years. A market for them in the United States was created when the harsh 1997 winter in Florida devastated domestic orange production, increasing prices and decreasing availability. Clementines are typically sold in net bags contained in small wooden or cardboard boxes. They sell in large numbers from mid-November through January, giving them the nickname "Christmas oranges" in some markets.
Clementines lose their desirable seedless characteristic when they are cross-pollinated with other fruit. To prevent this, in 2006 growers such as Paramount Citrus in California threatened to sue local beekeepers to keep bees away from their crops.