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.
|Malayan kumquat foliage and fruit|
"Kumquat" in Chinese characters
|Literal meaning||"golden orange"|
|Nutritional value per 100 g (3.5 oz)|
|Energy||296 kJ (71 kcal)|
|Dietary fiber||6.5 g|
|Vitamin A equiv.|
|Pantothenic acid (B5)|
|†Percentages are roughly approximated using US recommendations for adults. |
Source: USDA Nutrient Database
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 The earliest historical reference to kumquats appears in literature of China from the 12th century.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 into as few as two species. Historically they were viewed as falling within the genus Citrus, but the Swingle system of citrus taxonomy elevated them to their own genus, Fortunella. Recent phylogenetic analysis suggests they do indeed fall within Citrus. Swingle divided the kumquats into two subgenera, the Protocitrus, containing the primitive Hong Kong kumquat, and Eufortunella, comprising the round, oval kumquat, Meiwa kumquats, to which Tanaka added two others, the Malayan kumquat and the Jiangsu kumquat. Chromosomal analysis suggested that Swingle's Eufortunella represent a single 'true' species, while Tanaka's additional species were revealed to be likely hybrids of Fortunella with other Citrus, so-called Citrofortunella. Recent genomic analysis concluded there was only one true species of kumquat, but the analysis did not include the Hong Kong variety seen as a distinct species in all earlier analyses.
The round kumquat, Marumi kumquat or Morgani kumquat (retaining the name Citrus japonica or Fortunella japonica when kumquats are divided into multiple species), is an evergreen tree that produces edible golden-yellow fruit. 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 in Luxembourg 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.
The oval kumquat or Nagami kumquat (Citrus margarita or Fortunella margarita if dividing Eufortunella kumquats into separate species) is ovoid in shape and typically 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.
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.
The Meiwa kumquat (Citrus crassifolia or Fortunella crassifolia) was brought to Japan from China at the end of the 19th century, it has seedy oval fruits and thick leaves, and was characterized as a different species by Swingle. Its fruit is typically eaten skin and all.
Hong Kong kumquatEdit
The Hong Kong kumquat (Citrus hindsii or Fortunella hindsii) produces only pea-sized bitter and acidic fruit with very little pulp and large seeds. It is primarily grown as an ornamental plant, though it is also found in southern China growing in the wild. Not only is it the most primitive of the kumquats, but with the kumquats being the most primitive citrus, Swingle described it as the closest to the ancestral species from which all citrus evolved. While the wild Hong Kong kumquat is tetraploid, there is a commercial diploid variety, the Golden Bean kumquat with slightly larger fruit.
The Jiangsu kumquat or Fukushu kumquat (Citrus obovata or Fortunella obovata) bears edible fruit that can be eaten raw, as well as made into jelly and marmalade. The fruit can be round or bell-shaped 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. Chromosomal analysis showed this variety to be a likely hybrid.
The Malayan kumquat (Fortunella polyandra or in Citrus, Tanaka's Fortunella swinglei), from the Malay Peninsula where it is known as the "hedge lime" (limau pagar), is another hybrid, perhaps a limequat. It has a thin peel on larger fruit compared to other kumquats.
Cultivation and usesEdit
Kumquats are much hardier than 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 pollinationEdit
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
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A mature specimen on rough lemon rootstock at Oneco, Florida, in 1901, bore a crop of 3,000 to 3,500 fruits.
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- Centennial at the Citrus Variety Collection
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- "×Citrofortunella microcarpa". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA). Retrieved 1 June 2014.
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- Fruits of warm climates
- Fortunella crassifolia Swingle – Fruits and Seeds Flavon's Wild herb and Alpine plants
- International Code of Botanical Nomenclature (Tokyo Code)