The Kumquat is a small fruit-bearing tree in the genus Fortunella. Its fruit closely resembles those of the related genus Citrus, and, like that genus, it is also classified in the flowering plant family Rutaceae.
It is a slow-growing, evergreen shrub or small tree, from 2.5-4.5 m tall, with dense branches, sometimes bearing small thorns. The leaves are dark glossy green, and the flowers pure white, similar to citrus flowers, borne singly or clustered in the leaf-axils.

Kumquats originated in China (noted in literature there in the 12th century), and have long been cultivated there and in Japan. They were introduced to Europe in 1846 by Robert Fortune, collector for the London Horticultural Society, and shortly thereafter into North America. Originally placed in the genus Citrus, they were transferred to the genus Fortunella in 1915.

There are four species currently accepted, including Hong Kong Wild Kumquat (Fortunella hindsii), Marumi Kumquat (Fortunella japonica), Meiwa Kumquat (Fortunella crassifolia), and Nagami Kumquat (Fortunella margarita).

In appearance the kumquat fruit (generally called simply "kumquat") resembles a miniature oval or oblong orange, 3-5 cm long and 2-4 cm wide. Depending on variety, peel color ranges from yellow to red. A Nagami kumquat is oval and has a yellow skin, while a Marumi kumquat is round with an orange-colored skin.

Kumquat fruit is generally in season from late November to February, and can be found in most food markets with other produce.

Climate

They are much hardier than citrus plants such as oranges. The 'Nagami' kumquat requires a hot summer, ranging from 25 ºC to 38º C, but can withstand frost down to about −10 °C without injury. It grows in the tea regions of China where the climate is too cold for other citrus fruits, even 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 through several weeks of subsequent warm weather without putting out new shoots or blossoms. Despite their ability to survive low temperatures, as in the vicinity of San Francisco, California, the kumquat trees grow better and produce larger and sweeter fruits in warmer regions.


Propagation

Kumquats are rarely grown from seed as they do not do well on their own roots. In China and Japan they are grafted onto the trifoliate orange (Poncirus trifoliata). This has been found the best rootstock for kumquats in northern Florida and California and for dwarfing for pot culture. Sour orange and grapefruit are suitable rootstocks for southern Florida. Rough lemon is unsatisfactory in moist soils and tends to be too vigorous for the slow-growing kumquats.


Uses

Kumquats are frequently eaten whole; the skin is sweet and the inner fruit tart. The juicy center is often too sour to eat and is thrown away after the rind is nibbled off and consumed. The fruit is considered ripe when it reaches a yellowish-orange stage, and has just shed the last tint of green. A variety of kumquat grown in Hong Kong has rather sweet rind compared to the rind of other citrus fruits.

Culinary uses include: candying and kumquat preserves, marmalade, and jelly. Kumquats appear more commonly in the modern market as a martini garnish, replacing the classic olive. A liqueur can also be made by soaking kumquats in vodka or other clear spirit.

The Cantonese often preserve kumquats in salt. A batch of the fruit is buried in dry salt inside a glass jar. Over time, all the juice from the fruit is extracted through osmosis into the salt. The fruits in the jar become 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.

Yup!! They make it sour added some salt.. I saw they do it in the drama I watched last 3 years.. It looks so delicious..

Lots of Chinese folks are into this fruit. If you visit Chinese households (especially if they are over 45), there's like a 50-50 chance you'll see a Kumquat plant. I never see them actually picking them and eating them, though. Maybe they don't want to have the plant looking bare.

I do know that they are de-seeded, salted and dried and then sold in packets in some Asian shops, though. actually quite tasty, but I have never had them fresh. Anyone had them fresh?

I just purchased my first kumquats this past week, just a little contaiber from the grocery store. I cant say what variety they were. It was a little weird at first eating the peel... its hard to eat a citrus peel when for so many years we are told to peel them. It was a lot like a mild orange, lots of seeds, pulpy and sour. I am still on the fence, but I do like them and will get a plant or two in April. I think its a fruit you either like a lot... or grow to like. I actually find I like the peel/skin better than the flesh inside!

Late at night when I have the munchies but don't want to get chubby, I sometimes eat dried fruit like raisins, craisins, apricots, and even kumquats. I guess the salt and the sugar are still there, but at least with the sugar it is natural. I think it is better than refined sugar no matter what. Kumquats are better than raisins or craisins because they're bigger. You feel like you're eating something substantial. Actually fresh fruit in general is a great late night snack but that is sort of off topic, so I'll start another thread. Look for me, loyal readers!

In orchard plantings, kumquats on trifoliate orange can be set 8 to 12 ft (2.4-3.65 m) apart, or they may be spaced at 5 ft (1.5 m) in hedged rows 12 ft (3.65 m) apart. For pot culture, they must be dwarfed; must not be allowed to become pot-bound, and need faithful watering to avoid dehydration and also need regular feeding.