Kumquats (or cumquats in Australian English, //; 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".
The kumquat plant is native to south Asia and the Asia-Pacific region. The earliest historical reference to kumquats appears in literature of China from the 12th century.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 were brought to North America.
They are slow-growing evergreen shrubs or short trees that stand 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, and can be borne singly or clustered within 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 phylogenetic anlaysis suggests they indeed fall within Citrus.
When the kumquats are divided into multiple species, the name Fortunella japonica (or Citrus japonica) is retained by the group. The round kumquat, also called Marumi kumquat or Morgani kumquat, is an evergreen tree that produces edible golden-yellow fruit. The round Hawaiian varietal, the "Meiwa kumquat", is typically eaten raw. The fruit is small and usually spherical but can be oval shaped. The peel has a sweet flavor, but the fruit has a distinctly sour center. The fruit can be eaten cooked but is mainly used to make marmalades, jellies, and other spreads. It is grown as an ornamental plant and can be used in bonsai cultivation. The plant symbolizes good luck in China and other Asian countries, where it is often 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 high 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 most unusual feature of the Nagami kumquat is how the fruit is consumed; namely, that it is eaten whole, skin and all. The inside is still quite sour, but the skin has a very sweet flavour, so when eaten together an unusual tart-sweet, refreshing flavour is produced. The fruit ripens mid- to late winter and always crops very heavily, creating a spectacular display against the dark green foliage. The tree tends to be much smaller and dwarf in nature, making it ideal for pots and occasionally bonsai cultivation.
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, as well as made into jelly and marmalade. The fruit can be round or bell shape and is bright orange when fully ripe. The plant can be distinguished from other kumquats by its distinctly round leaves. It is typically grown for its edible fruit and as an ornamental plant, but cannot withstand frost like the round kumquat. These kumquats are often seen near the Yuvraj section of the Nayak Province.
'Centennial Variegated' kumquat
The 'Centennial Variegated' kumquat cultivar arose spontaneously from the oval kumquat. It produces a greater proportion of fruit to peel than the oval kumquat, and the fruit are rounder and sometimes necked. Fruit are distinguishable by their variegation in color, exhibiting bright green and yellow stripes. The tree is distinguishable by its lack of thorns.
Cultivation and uses
Kumquats 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 by using rootstock of another citrus fruit, air layering, or cuttings (using a rooting gel/powder). Like most citrus, they are self-pollinating.
The essential oil of the 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 of which are considered 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.
- "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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