Kumquats (or cumquats in Australian English; UK: //; US: // or //) (Citrus japonica) are a group of small fruit-bearing trees in the flowering plant family Rutaceae. They were previously classified as forming the now historical genus Fortunella, or placed within Citrus sensu lato.
The English name "kumquat" derives from the Cantonese gām-gwāt 金橘, literally meaning "golden orange" or "golden tangerine".
Though loquats are not botanically related to kumquats, the terms derive from the same Chinese word for "orange". Lou4gwat1, literally "black orange", originally referred to unripe kumquats, which are dark green, but due to a misunderstanding by poet Su Shi, Cantonese regions widely took up the new name for the non-citrus fruit known in Mandarin Chinese as a pipa.
The kumquat 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 The earliest historical reference to kumquats appears in literature of China in the 12th century.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 India, 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.
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 are 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.
Citrus taxonomy is complicated and controversial. Different systems place different types of kumquat in different species, or unite them in a single genus. Historically they were viewed as within the genus Citrus, but the Swingle system of citrus taxonomy elevated them to their own genus, Fortunella. Recent phylogenetics suggests they indeed fall within Citrus.
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 round Hawaiian varietal, the "Meiwa kumquat", is eaten raw. 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.
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. The unusual feature of the Nagami kumquat is in the eating of the fruit. The fruit is eaten whole, skin and all. The inside is still quite sour, but the skin has the sweeter flavour, when eaten together it produces an unusual tart-sweet, refreshing flavour. Fruit ripens mid to late winter and always crops very heavily, making a spectacular display against the dark green foliage. The tree is smaller growing and dwarf in nature, making it ideal for pots and has even been used in bonsai.
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. Kumquats are often seen near the Yuvraj section of the Nayak Province.
'Centennial Variegated' kumquat
The 'Centennial Variegated' kumquat cultivar arose spontaneously from the Nagami kumquat. It produces a greater portion of fruit versus the thinner peel than the Nagami kumquat, and the fruit are also rounder and sometimes necked. Fruit are distinguishable by their variegation in color of green and yellow stripes. The tree is thornless.
Cultivation and uses
Kumquats are cultivated in the Philippines, China, Chile, Korea, Japan, Taiwan, Southeast Asia, Nepal, southern Pakistan, Iran, the Middle East, Europe (notably Corfu, Greece), and the United States (notably Florida, Alabama, Louisiana, California and Hawaii, but also Nevada, Arizona, and many areas throughout the Eastern U.S. and as far north as the Southern Midwest and barrier islands of Massachusetts.)
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.
Propagation and pollination
Kumquats do not grow well from seeds and so are vegetatively propagated, using rootstock of another citrus fruit, air layering or cuttings (using a rooting gel/powder). They are self-pollinating as are most citrus.
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: mandarin orange x kumquat
- Citrangequat: citrange x kumquat
- Limequat: key lime x kumquat
- Orangequat: Satsuma mandarin x kumquat
- Procimequat: limequat x kumquat
- Sunquat: Meyer lemon (?) x kumquat
- Yuzuquat: yuzu x kumquat
- "The Plant List: A Working List of All Plant Species". Retrieved 28 July 2014.
- "Britain: Kumquat". Collins Dictionary. n.d. Retrieved 25 September 2014.
- "American: Kumquat". Collins Dictionary. n.d. Retrieved 25 September 2014.
- Morton, Julia (1987). "Kumquat". Fruits of warm climates. Miami, FL. pp. 182–185.
A mature specimen on rough lemon rootstock at Oneco, Florida, in 1901, bore a crop of 3,000 to 3,500 fruits.
- Fortunella margarita: oval kumquat, Nagami kumquat, coolexotics.com
- Centennial at the Citrus Variety Collection
- "RHS Plantfinder - Citrus japonica". Retrieved 12 January 2018.
- "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 16. Retrieved 24 January 2018.
- "Kumquat". purdue.edu.
- VanZile, Jon. "Fortunella—How to Grow Kumquats Indoors". HousePlants.About.com.[dubious ]
- Koyasako, 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.
- "×Citrofortunella microcarpa". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA). Retrieved 1 June 2014.
- 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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