Kumquats or cumquats are a group of small fruit-bearing trees in the flowering plant family Rutaceae, either forming the genus Fortunella, or placed within Citrus sensu lato. The edible fruit closely resembles that of the orange (Citrus sinensis), but it is much smaller and ovular, being approximately the size and shape of a large olive. The English name "kumquat" derives from the Cantonese pronunciation gam1 gwat1 (given in Jyutping romanization).
They are slow-growing evergreen shrubs or short trees, from 2.5 to 4.5 meters (8 to 15 ft) tall, with dense branches, sometimes bearing small thorns. The leaves are dark glossy green, and the flowers white, similar to other citrus flowers, borne singly or clustered in the leaf-axils. Depending on size, the kumquat tree can produce hundreds or even thousands of fruits each year. The tree can be hydrophytic, with the fruit often found floating on water near shore during the ripe season.
The plant is native to south Asia and the Asia-Pacific region. The earliest historical reference to kumquats appears in literature of China in the 12th century. They have long been cultivated in Japan, Taiwan, the Philippines, and southeast Asia. They were introduced to Europe in 1846 by Robert Fortune, collector for the London Horticultural Society, and shortly thereafter into North America.
Carl Peter Thunberg originally classified the kumquats as Citrus japonica in his 1784 book Flora Japonica. In 1915, Walter T. Swingle reclassified them in a segregate genus, Fortunella, named in honor of Robert Fortune. Seven species of Fortunella have generally been recognized—F. japonica, F. margarita, F. crassifolia, F. hindsii, F. obovata and F. polyandra, as well as the recently described F. bawangica . The Flora of China returns the kumquat to Citrus and combines the species into the single species as Citrus japonica.
Round kumquat 
When the kumquats are divided into multiple species, the name Fortunella japonica (or Citrus japonica) is retained by this group. The round kumquat also called Marumi kumquat or Morgani kumquat, is an evergreen tree, producing edible golden-yellow fruit. The fruit is small and usually round but can be oval shaped. The peel has a sweet flavor but the fruit has a sour center. The fruit can be eaten cooked but is mainly used to make marmalades and jellies. It is grown as an ornamental plant and can be used in bonsai. The plant symbolizes good luck in China and other Asian countries, where it is kept as a houseplant and given as a gift during the Lunar New Year. Round kumquats are more commonly cultivated than other species due to their cold tolerance.
Oval kumquat 
When the kumquats are divided into multiple species, the name Fortunella margarita (or Citrus margarita) is used for this group. The oval kumquat is also called the Nagami kumquat.
Jiangsu kumquat 
When the kumquats are divided into multiple species the name Fortunella obovata (or Citrus obovata) is used for this group. The Jiangsu kumquat or Fukushu kumquat bears edible fruit that can be eaten raw. The fruit can be made into jelly and marmalade. The fruit can be round or bell shaped; it is bright orange when fully ripe. It may be distinguished from other kumquats by its round leaves. It is grown for its edible fruit and as an ornamental plant. It cannot withstand frost.
Cultivation and uses 
Kumquats are cultivated in China, South Korea, North Korea, Taiwan, Southeast Asia, Japan, the Middle East, Europe (notably Corfu, Greece), southern Pakistan, and the southern United States (notably Florida, Louisiana, Alabama) and California.
They are much hardier than other citrus plants such as oranges. The 'Nagami' kumquat requires a hot summer, ranging from 25 °C to 38 °C (77 °F to 100 °F), but can withstand frost down to about −10 °C (14 °F) without injury. They grow in the tea hills of Hunan, China, where the climate is too cold for other citrus fruits, even the Mikan (also known as the Satsuma) orange. The trees differ also from other citrus species in that they enter into a period of winter dormancy so profound that they will remain in it through several weeks of subsequent warm weather without putting out new shoots or blossoms. Despite their ability to survive low temperatures, kumquat trees grow better and produce larger and sweeter fruits in warmer regions.
Kumquats do not grow well from seeds and so are vegetatively propagated, using rootstock of another citrus fruit.
Kumquats are often eaten raw. As the rind is sweet and the juicy center is sour, the raw fruit is usually consumed either whole—to savor the contrast—or only the rind is eaten. The fruit is considered ripe when it reaches a yellowish-orange stage and has just shed the last tint of green.
Culinary uses include candying and kumquat preserves, marmalade, and jelly. Kumquats can also be sliced and added to salads. In recent years kumquats have gained popularity as a garnish for cocktail beverages, including the martini as a replacement for the more familiar olive. A kumquat liqueur mixes the fruit with vodka or other clear spirit. Kumquats are also being used by chefs to create a niche for their desserts and are common in European countries.
The Cantonese often preserve kumquats in salt or sugar. A batch of the fruit is buried in dry salt inside a glass jar. Over time, all the juice from the fruit is diffused into the salt. The fruit in the jar becomes shrunken, wrinkled, and dark brown in color, and the salt combines with the juice to become a dark brown brine. A few salted kumquats with a few teaspoons of the brine/juice may be mixed with hot water to make a remedy for sore throats. A jar of such preserved kumquats can last several years and still keep its flavor.
Variants of the kumquat are grown specially in India.
Potted kumquat trees at a kumquat liqueur distillery in Corfu.
Bags of kumquat for sale at the Kumquat Festival
Shelves of kumquat jelly and kumquat butter at the 2011 Kumquat Festival
The essential oil of kumquat peel contains much of the aroma of the fruit, and is composed principally of limonene, which makes up around 93% of the total. Besides limonene and alpha-pinene (0.34%), both monoterpenes, the oil is unusually rich (0.38% total) in sesquiterpenes such as α-bergamotene (0.021%), caryophyllene (0.18%), α-humulene (0.07%) and α-muurolene (0.06%), and these contribute to the spicy and woody flavor of the fruit. Carbonyl compounds make up much of the remainder, and these are responsible for much of the distinctive flavor. These compounds include esters such as isopropyl propanoate (1.8%) and terpinyl acetate (1.26%); ketones such as carvone (0.175%); and a range of aldehydes such as citronellal (0.6%) and 2-methylundecanal. Other oxygenated compounds include nerol (0.22%) and trans-linalool oxide (0.15%).
Hybrid forms of the kumquat include the following:
- Calamondin: tangerine + kumquat
- Citrangequat: citrange + kumquat
- Limequat: key lime + kumquat
- Mandarinquat: mandarin + kumquat
- Orangequat: Satsuma mandarin + kumquat
- Procimequat: limequat + kumquat
- Sunquat: lemon + kumquat
- Yuzuquat: yuzu + kumquat
Though loquats are not botanically related to kumquats, the terms originate in the same Chinese word designating "orange".
- Morton, Julia (1987). "Kumquat". Fruits of warm climates. A mature specimen on rough lemon rootstock at Oneco, Florida, in 1901, bore a crop of 3,000 to 3,500 fruits. pp. 182–185.
- Zhang Dianxiang, Thomas G. Hartley, David J. Mabberley, Rutaceae in Flora of China 11: 51-97 (2008)
- Fortunella margarita: oval kumquat, Nagami kumquat, coolexotics.com
- Koyasako, A, A.; Bernhard, R.A. (1983). "Volatile Constituents of the Essential Oil of Kumquat". Journal of Food Science (Wiley & Sons) 48 (6): 1807–1812. doi:10.1111/j.1365-2621.1983.tb05090.x.
Further reading 
- Burkill, I. H. (1931). An enumeration of the species of Paramignya, Atalantia and Citrus, found in Malaya. Gard. Bull. Straits Settlem. 5: 212–220.
- Mabberley, D. J. (1998). Australian Citreae with notes on other Aurantioideae (Rutaceae). Telopea 7 (4): 333–344. Available online (pdf).
- Fruits of warm climates
- Fortunella crassifolia Swingle - Fruits and Seeds Flavon's Wild herb and Alpine plants
- International Code of Botanical Nomenclature (Tokyo Code)
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