Mandarin orange

The mandarin orange (Citrus reticulata) is a small, round citrus fruit, commonly called just a mandarin. It is considered a distinct type of orange and is typically eaten fresh or added to fruit salads. The fruit is small and flattened at the poles, unlike the rounder sweet orange (which is actually a hybrid of mandarin and pomelo). Its flavor is sweeter and more intense than that of a common orange. When ripe, a mandarin is firm to slightly soft, feels heavy for its size, and has a bumpy, pebbly skin. The peel is thin and loose, with little of the white pith, making it easy to peel and separate into segments. Hybrids have these traits to a lesser extent. The tree is sensitive to cold and grows best in tropical and subtropical climates.

Genetic research shows that the wild mandarin is one of the original citrus species. Through natural hybridization and breeding, it became the ancestor of many hybrid citrus varieties. Along with the citron and pomelo, it is a parent of the most commercially important citrus hybrids. While the original wild mandarin was bitter, most modern commercial strains come from crosses with the pomelo, which gave them sweet fruit.

The name "mandarin orange" comes from the Swedish term *mandarin apelsin* (where *apelsin* derives from German *Apfelsine*, meaning "Chinese apple"), first recorded in the 1700s. The French first used the word "mandarine" for this fruit, borrowing it from the Imperial Chinese term "mandarine." The reason for this name is unclear. The scientific name *Citrus reticulata* comes from Latin, where *reticulata* means "netted."

The mandarin tree is a moderate size, reaching about 7.6 meters (25 feet) tall. Its trunk and main branches have thorns. The leaves are shiny, green, and relatively small, with short leaf stalks that are almost wingless or only slightly winged. Flowers grow singly or in small clusters in the leaf axils. Citrus trees are usually self-fertile (needing only a bee to move pollen within the same flower) or parthenocarpic (not needing pollination, so seedless, like the satsuma). A mature tree can produce up to 79 kilograms (175 pounds) of fruit.

Mandarin fruits are small, 40 to 80 millimeters (1.6 to 3.1 inches) across. Their color ranges from orange to yellow-orange or red-orange. The thin skin peels off easily, a major advantage over other citrus fruits. Like other citrus, the segments separate easily. The fruit may be seedless or have a few seeds. They can be eaten whole or squeezed for juice.

In 2026, the genome of the Ponkan mandarin was re-annotated as part of a study of three major citrus crops. The updated annotation had a BUSCO completeness score of about 99.5%, identifying 25,162 protein-coding genes, 42,833 mRNAs, and 18,751 alternative-splicing events.

The wild mandarin is one of the pure ancestral citrus types, evolving in a limited area of South China and Vietnam. Mandarins appear to have been domesticated at least twice, in the northern and southern Nanling Mountains, from separate wild subspecies. Wild mandarins still grow there, including Daoxian mandarins (sometimes called *Citrus daoxianensis*) and some from the group known as 'Mangshan wild mandarins.' This group includes both true mandarins (the southern subspecies) and the genetically distinct Mangshanyegan. The wild mandarins lack the pomelo DNA found in domestic mandarins, but they do have a small amount (about 1.8%) of DNA from the ichang papeda, which grows wild in the same region.

The Nanling Mountains contain northern and southern genetic groups of domestic mandarins. Both groups have similar sugar levels to their wild relatives but much lower citric acid levels (in some cases nearly 90-fold lower). The two groups show different patterns of pomelo DNA, have different historical population histories, and are most closely related to different wild mandarins, indicating two separate domestications. All tested domestic varieties belong to one of these two groups. The northern group includes varieties like Nanfengmiju, Kishu, and Satsuma, which produce larger, redder fruit. The southern group includes Willowleaf, Dancy, Sunki, Cleopatra, King, and Ponkan, which produce smaller, yellower fruit.

In the Tanaka classification system, domestic mandarins and similar fruits were split into many species, giving distinct names to cultivars like willowleaf mandarins (*C. deliciosa*), satsumas (*C. unshiu*), and tangerines (*C. tangerina*). Under the Swingle system, all these are considered varieties of a single species, *Citrus reticulata*. Hodgson grouped them into several categories: common (*C. reticulata*), Satsuma, King (*C. nobilis*), Mediterranean (willowleaf), small-fruited (*C. indica*, *C. tachibana*, *C. reshni*), and mandarin hybrids. In the genomic-based taxonomy of Ollitrault et al., only pure wild-type mandarins would be classified as *C. reticulata*, while most mandarins with pomelo DNA would be considered varieties of the hybrid bitter orange, *C. aurantium*. Genetic analysis suggests that continental mandarins are a single species, varying due to hybridization.