Kumquat
Citrus crassifolia and other spp.
Family: Rutaceae
Kumquat taxonomy is complicated and controversial. Different systems place various types of kumquats in different species or unite them into as few as two species. Botanically, many of the varieties of kumquats are classified as their own species, rather than a cultivar. 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 fall within Citrus.
The kumquat plant is native to Southern China. The historical reference to kumquats appears in literature of China from at least the 12th century. They have been cultivated for centuries in other parts of East Asia, South Asia, and Southeast Asia. They were introduced into Europe in 1846 by Robert Fortune, collector for the London Horticultural Society, and are now found across the world.
TYPES OF KUMQUATS
Hong Kong kumquat (Citrus 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 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.
Meiwa kumquat (Citrus crassifolia) brought to Japan from China at the end of the 19th century. It is a hybrid of Nagami and Marumi. 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.
Nagami kumquat (Citrus margarita) is ovoid in shape and typically eaten whole, skin and all. The inside is still quite sour, but the skin has a very sweet flavor, 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.
Nordmann seedless (Citrus margarita) a seedless sport of the Nagami kumquat. It is similar to Nagami but with a slightly different shape and lighter skin.
centennial variegated (Citrus margarita) is another sport of the Nagami. It originated from the open pollination of a Nagami kumquat tree. The fruits are striped light green and yellow when underripe, and turn orange and lose their stripes when they ripen. They are oval-shaped, necked, 2.5 inches long and have a smooth rind. They mature in winter.
Round kumquat, Marumi kumquat, or Morgani kumquat (Citrus japonica) 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. The tree can be used in bonsai cultivation. The plant symbolizes good luck in China, where it is often kept as a houseplant and given as a gift during the Lunar New Year in China. Round kumquats are more commonly cultivated than other species due to their high cold tolerance.
Jiangsu kumquat or Fukushu kumquat (Citrus 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; it cannot withstand frost, however, unlike the round kumquat which has a high cold tolerance. These kumquats are often seen near the Yuvraj section of the Nayak Province. Chromosomal analysis showed this variety to be a likely hybrid.
Malayan kumquat (Citrus x 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.
Puchimaru kumquat (Citrus japonica) is a seedless or virtually seedless Japanese kumquat cultivar. It is resistant to citrus canker and citrus scab. The fruit weighs 11–20 grams and is ellipsoid in shape. It has a dark orange rind which is 4 millimeters thick. The juice content is relatively low. The oil glands are somewhat large and conspicuous. It ripens in January.
Hybrid forms of the kumquat include the following:
Calamansi: 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
USES
Kumquat are almost always used fresh, often eaten with the peel and all. They can also be used for their juice though oranges, if available, are usually better for this use. Limequats, on the other hand, make excellent cocktails.
Here is an article with 13 chefs sharing their favorite recipes for kumquats.
GROWING
Kumquats should be planted in amended soil, in full sun. Plant appreciate mulching so long as you don’t bury the root flare of the tree.
How often you water depends on your soil, and the method of watering that you use. In winter, once a month deeply is sufficient. As it warms up in the spring, go to every other week, again…deeply. In the height of summer you might water once a week to every two weeks, deeply. Pull back watering in September to harden off new growth.
Feed citrus trees with an organic, general purpose fertilizer once a month February through August. Or you can feed three times a year in February, May, and August.
Pruning isn’t necessary, in our opinion, except for grafted trees—prune any branches that emerge from below the graft scar, as these branches will not produce the fruits you aim to grow, but from the root stock.
Kumquat varieties tend to be much more cold hardy than most citrus. But in colder areas, if the temperature gets below 15°F, protect plants from the cold.
You might notice a few species of butterfly on your trees, and their larvae. Citrus trees provide as larval hosts for a few species of swallowtail, especially the giant swallowtail (Papilio cresphontes)—the larvae look like bird poop, an excellent camouflage to protect themselves from predators.