A kumquat is a fruit which resembles a miniature orange. It is sometimes mistaken for a citrus fruit, but actually belongs to the genus Fortunella. The kumquat, also spelled cumquat, has a thin, sweet skin with a tart, sour flesh. The kumquat can be eaten whole, though some find its juicy center to be too sour.
The kumquat is grown on a tree which is shrubby in appearance and usually about 8 to 15 feet (2.4 – 4.5 meters) tall. The kumquat tree has dark, glossy green leaves and bears white flowers. The fruit itself is oval and oblong or round and ranges from golden yellow to reddish-orange in color when ripe.
The kumquat is believed to be native to China, as it was described in Chinese literature as early as 1178. Kumquat trees require a warm summer to grow, but can withstand 10 to 15 degrees of frost without injury and enter into a period of winter dormancy that can last into several weeks of warmer weather. The kumquat can therefore be grown in regions too cold for citrus fruits, such as the tea region of China, although fruits from warmer regions grow to a larger size and taste sweeter.
The kumquat is rarely grown from seed, as the trees do not survive long on their own roots. In China and Japan, as well as Florida and California, grafting them onto the trifoliate orange produces the best plants. They are also sometimes grafted onto sour orange and grapefruit.
Four species of kumquat are currently accepted by horticultural societies and used for food. The Hong Kong Wild kumquat (Fortunella hindsii) grows on a thorny shrub native to Hong Kong and adjacent areas of China and is gathered there while in season, but only used decoratively in other parts of the world. The Marumi (Fortunella japonica) kumquat is yellow and round. The Meiwa (Fortunella crassifolia) is possibly a hybrid of the two and has a thicker, sweeter pulp. Most common in the United States is the oval-shaped Nagami kumquat (Fortunella margarita), which is in season from October to January.
The kumquat is often candied or used to make preserves and jelly. In China, kumquats are sometimes preserved whole in sugar syrup and sold in restaurants as desserts, or preserved in salt and served with the brine mixed with hot water to treat sore throats. A kumquat liqueur can be made be soaking the fruit in a clear spirit. Kumquats are also added to salads, as well as used to make marmalades and sauces.