Common Name: Round Kumquat

General Information

Citrus japonica is a much-branched, spiny, evergreen shrub or a small tree that can grow up to 5 metres tall with a trunk up to 20cm in diameter[].
The plant is often cultivated, especially in China, for its edible fruit and also has a range of medicinal applications. It is sometimes grown as an ornamental[].

Known Hazards

None known

Botanical References

,

Range

E. Asia - China, Japan.

Habitat

Evergreen broad-leaved forests; 600 - 1,000 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	2.50 m
Pollinators	Insects
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Citrus japonica is native to the subtropical climate of southeastern China. It is not a very cold-hardy plant, when dormant it can tolerate short periods where temperatures fall to around -5[]. The new growth is much more susceptible to cold and can be badly damaged at around 0°c[]. Kumquats are hardier than the various other cultivated Citrus species (such as the oranges and the lemons) since they cease growth when temperatures drop below 13°c. For best results, however, it is best to grow them in a climate with warm to hot summers and winter temperatures that do not fall lower than between 4 - 10°c[]. This is because the fruit is sweeter when it ripens in warm conditions[]
Prefers a moderately heavy loam with a generous amount of compost and sand added and a very sunny position[]. Prefers a pH of 5 to 6[]. Plants are intolerant of water logging[].
The young growth in spring, even on mature plants, is frost-tender and so it is best to grow the plants in a position sheltered from the early morning sun[].
Kumquats are widely cultivated, especially in China, for their edible fruit. There are many named varieties, and these can usually be divided into two main cultivar groups[].
Round Kumquat Group (Formerly known as Fortunella japonica). These are usually trees 2 - 5 metres tall. The orangish yellow to orangish red, globose fruit is 15 - 25mm in diameter with a sweet-tasting skin up to 2mm thick[],
Oval Kumquat Group (Formerly known as Fortunella margarita). These are usually trees around 3 metres tall. The orangish yellow to orangish red, ellipsoid to ovoid-ellipsoid fruit is 20 - 35mm in diameter with a sweet-tasting skin around 2mm thick and an acidic flesh in 4 - 5 segments[].

Edible Uses

Fruit - raw or cooked[]. They can also be used in jellies, preserves etc or as a flavouring[]. The whole fruit, including the skin, can be eaten raw - the fruit is very acid whilst the peel has a sweet flavour and the two flavours combine well to make a very tasty food[, , ]. It is best to first squeeze and massage the fruit in order to combine the flavours of the flesh and the rind[]. The skin of the round kumquat is golden-yellow, smooth, thinner and somewhat sweeter than that of the oval kumquat[].
The fruit is rich in pectin, the inner peel containing about 10%[]. It makes excellent marmalades and jellies[]. Vitamin C content is up to 0.24 mg/cc[].
After ripening the fruit gradually loses water content, becomes richer in flavour and is then at its best for making preserves[].
The bright orange to red, globose to slightly oblate fruit is around 9 - 10mm in diameter in wild forms, and 15 - 35mm in cultivated forms[].

Medicinal

The plant is antiphlogistic, antivinous, carminative, deodorant, stimulant[, ].

The fresh fruit is antitussive and expectorant - in Vietnam it is steamed with sugar candy and used in the treatment of sore throats[]. It is said to be very good for infants[].

The leaves and fruit contain an essential oil, whilst the fruit also contains sugars and organic acids[].

Other Uses

The fresh leaves and young twigs yield 0.21% essential oil that might be suitable for perfumery[].

Propagation

Seed - best sown as soon as it is ripe in a warm airy position in a greenhouse. When they are large enough to handle, prick out the seedlings into individual pots and grow them on in a greenhouse for at least their first two winters. Plant out in late spring or early summer after the last expected frosts and give some winter protection from the cold for a year or two.