Dimocarpus longan

Dimocarpus longan

The longan (Dimocarpus longan Lour.) is an arboreal species belonging to the Sapindaceae family.

Systematics –
From a systematic point of view it belongs to:
Eukaryota Domain,
Kingdom Plantae,
Magnoliophyta Division,
Magnoliopsida class,
Sapindales Order,
Sapindaceae family,
Genus Dimocarpus,
D. longan species.
The terms are synonymous:
– Euphoria longan (Lour.) Steud .;
– Euphoria longana Lam .;
– Nephelium longana Cambess .;
– Nephelium long-yan Blume.

Etymology –
The term Dimocarpus comes from the Greek δίδυμος dídymos double, twin and καρπός carpόs fruit: reference to the twin fruits.
The specific longan epithet derives from the Chinese vernacular name long yan (from lóng dragon and yǎn eye) or long-ngan: dragon eyes, referring to the appearance of spherical fruits, which grow in clusters.

Geographic Distribution and Habitat –
Longan is a plant native to China and widespread in eastern Asia, China, India, Sri Lanka, Myanmar, Thailand, Cambodia, Laos, Vietnam, Malaysia, Indonesia, the Philippines.
Its habitat is that of humid mountain forests; usually found in the undergrowth of primary forests, sometimes in secondary formations.

Description –
Longan is an upright, fast-growing, ornamental-looking evergreen tree with a branching canopy, usually growing 9-14 meters tall but can reach a height of 25 meters or more.
The trunk can be 1 meter in diameter.
The leaves are dark green, lanceolate and opposite in shape.
The flowers are small, carried in inflorescences.
The fruits that ripen in October are globose, have a diameter between 12 and 25 mm, with a thin and crumbly rind, yellow-brown to slightly reddish-brown in color and with a translucent pulp through which the black seed which is round in shape and hard.

Cultivation –
Longan is a widely grown plant in Southeast Asia. In Vietnam, the most popular cultivars are Tieuhue and Xuongcomvang. Kohala, Chompoo, Haew, and Biew Kiew are mainly grown in Australia.
This plant, although it grows in temperate and tropical zones, requires a distinct cold season of up to 3 months with virtually no frost in order to begin flowering so that it does not bear fruit well at low altitudes in the tropics.
Flowering is poor after a warm winter and in areas without a cool, clear season. In general it needs temperatures of the cold period of about 7 – 12 ° C, or a period of 2-3 months with temperatures of about 15 – 22 ° C and a short period of drought to stimulate flowering.
From fruit set onwards, high temperatures do not hinder development, but nights should not be warmer than 20 – 25 ° C.
The temperature range for growth is 7 – 36 ° C with the optimum between 18 – 30 ° C.
From the hygrometric point of view it is necessary a good humidity of the soil from fruit setting to maturity; the most suitable annual precipitation is about 1,500 – 2,000 mm. The annual rainfall range for growth is reported to be between 800 and 3,000 mm.
It is also a plant that takes advantage of light shade and grows well on most fertile soils as long as there is an abundance of moisture. The pH must be between 5.5 and 6, but can tolerate 5 – 8.
From the planting of the young seedlings, obtained from seed, 7-10 years must elapse to start bearing fruit, while the trees propagated by agamic way can bear fruit in 3-5 years.
With sufficient space, adult trees can produce 180-225 kg of fruit in good years. Bigger trees have bigger crops, but if the trees get too tall, harvesting is too difficult.
The longan also manifests an alternation of production with often a good year followed by 1 or 2 years of discharge.
Furthermore, trees are generally self-fertile.
As far as propagation is concerned, most of the longan trees are obtained from seed. After drying in the shade for 4 days, they should be planted immediately but no more than 2 cm deep, otherwise they can emit more than one sprout. Germination occurs within 7-10 days. The seedlings are transplanted into shaded nursery rows the following spring and placed in the field 2-3 years later during winter dormancy.
The trees are then grafted with the varieties available on the market.

Customs and Traditions –
Dimocarpus longan is a tropical fruiting tree called in southern China (龍眼 T, 龙眼 S, lóngyǎn P, Cantonese: long-ngan; literally “dragon’s eye”; Thai: ลำไย). It is also called guìyuán (桂圓 T, 桂圆 S) in Chinese, lengkeng in Indonesia, mata kucing (literally “cat’s eye”) in Malaysia, quả nhãn in Vietnamese, mora in Sinhalese (Sri Lanka) and equally longan in Tagalog.
The longan (“dragon’s eye”) is so named because of the fruit’s resemblance to an eyeball when shelled.
The fruits are eaten cooked or raw. They have a mucilaginous and whitish pulp, translucent and somewhat sweet, although not as tasty as the similar lychee (Litchi chinensis Sonn.).
The fruit is excellent when eaten raw and can also be dried, preserved in syrup, cooked in sweet and sour or in soups.
Longan fruits are widely eaten fresh although some claim that the fruit improves with cooking.
In China, most are canned, canned or dried. For drying, the fruits are first heated to shrink the pulp and facilitate peeling of the peel. Then the seeds are removed and the pulp dried over low heat.
The dried product has a strong, leathery and smoky flavor and is mainly used to prepare an infusion drunk for refreshment purposes.
There are also several medicinal uses.
The pulp of the fruit is given for stomach ailments, as a febrifuge and vermifuge, and is considered an antidote for the poison. A decoction of dried pulp is taken as a tonic and treatment for insomnia and neurasthenic neurosis.
In both North and South Vietnam, the “eye” of the longan seed is pressed against a snake bite in the belief that it will absorb the venom.
The leaves and flowers are sold in Chinese herbal markets, but they are not part of ancient traditional medicine. The leaves contain quercetin and quercitrin.
The seeds are administered to counteract heavy sweating and the pulverized kernel, which contains saponin, tannin and fat, acts as a hemostatic.
Among other uses, it should be remembered that the seeds, due to their saponin content, are used as soap bars (Sapindus saponaria L.) to prepare shampoo.
The seeds and rind are also burned as fuel.
The heartwood is reddish brown in color and is not clearly delimited by the lighter colored sapwood. The wood is strong, very hard, difficult to split, highly durable, dries easily but slowly with little or no degradation. It is used for poles, agricultural tools, furniture, construction, pipes, bearings, textile weaving supports and rifle butts.
Wood is not highly regarded as a fuel.

Preparation Method –
Logan fruit, as mentioned, is edible, and in Southeast Asia, where it is highly prized, it is often used for soups, snacks, desserts and sweet and sour sauces, or fresh or dried, sometimes canned. with syrup in supermarkets.
Fresh longan seeds can be boiled and eaten, with a distinctive nutty flavor.
Dried longans (Chinese: 圓 肉; pinyin: yuánròu; literally “round meat”) are often used in Chinese cuisine and Chinese sweet dessert soups. In Chinese dietetics and herbal medicine, the plant is believed to have an effect on relaxation. In contrast to the fresh fruit, which is white and juicy, the pulp of the dried longans is dark brown, almost black. In Chinese medicine, longan, much like lychee, is considered a “hot” fruit.

Guido Bissanti

Sources
– Acta Plantarum – Flora of the Italian Regions.
– Wikipedia, the free encyclopedia.
– Useful Tropical Plants Database.
– Conti F., Abbate G., Alessandrini A., Blasi C. (edited by), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.
– Pignatti S., 1982. Flora of Italy, Edagricole, Bologna.
– Treben M., 2000. Health from the Lord’s Pharmacy, Advice and experiences with medicinal herbs, Ennsthaler Editore.

Warning: Pharmaceutical applications and alimurgical uses are indicated for informational purposes only, they do not represent in any way a medical prescription; therefore no responsibility is taken for their use for curative, aesthetic or food purposes.