Longan (Dimocarpus longan). Leaves and fruits.

Longan - Dimocarpus longan

Dimocarpus longan, commonly known as the longan (/ˈlɒŋɑːnˈ/) and dragon's eye, is a tropical tree species that produces edible fruit. It is one of the better-known tropical members of the soapberry family Sapindaceae, to which the lychee and rambutan also belong. The fruit of the longan is similar to that of the lychee, but less aromatic in taste. It is native to tropical Asia and China.

Dimocarpus longan is a handsome, erect, fast-growing, evergreen tree with a many-branched crown.

Depending upon climate and soil type the tree may grow to over 100 feet (30 m) in height, but it typically stands 30–40 ft (9–12 m) in height and the crown is round. The trunk is 2.5 ft (0.8 m) thick with corky bark. The branches are long and thick, typically drooping. The bole can be 1 metre in diameter, sometimes with buttresses.

The leaves are oblong and blunt-tipped, usually 4–8 inches (10–20 cm) long and 2 in (5 cm) wide. The leaves are pinnately compounded and alternate. There are 6 to 9 pairs of leaflets per leaf and the upper surface is wavy and a dark, glossy-green.

The longan tree produces light-yellow inflorescences at the end of branches. The inflorescence is commonly called a panicle and are 4–18 in (10–46 cm) long, and widely branched. The small flowers have 5 to 6 sepals and petals that are brownish-yellow. The flower has a two-lobed pistil and 8 stamen. There are three flower types, distributed throughout the panicle; staminate (functionally male), pistillate (functionally female), and hermaphroditic flowers. Flowering occurs as a progression.

The fruit are circular and about 1 in (2.5 cm) wide; they hang in drooping clusters. The peel is tan, thin, and leathery with tiny hairs. The flesh is translucent, and the seed is large and black with a circular white spot at the base. This gives the illusion of an eye. The flesh has a musky, sweet taste, which can be compared to the flavor of lychee fruit.

The longan (from Cantonese lùhng-ngáahn 龍眼, literally 'dragon eye'), is so named because it resembles an eyeball when its fruit is shelled (the black seed shows through the translucent flesh like a pupil and iris). The seed is small, round and hard, and of an enamel-like, lacquered black.

Legend has it that the fruit got its name from a brave man named Longan, who defeated a dragon that terrorized a southern Chinese coastal town every August.

The fully ripened, freshly harvested fruit has a bark-like shell, thin, and firm, making the fruit easy to peel by squeezing the pulp out as if one were "cracking" a sunflower seed. When the shell has more moisture content and is more tender, the fruit becomes less convenient to shell. The tenderness of the shell varies due to either premature harvest, variety, weather conditions or storage conditions.

The longan is believed to originate from the mountain range between Myanmar and southern China. Other reported origins include Indonesia, India, Sri Lanka, upper Myanmar, north Thailand, Kampuchea (more commonly known as Cambodia), north Vietnam and New Guinea.

Its earliest record of existence draws back to the Han dynasty in 200 BC. The emperor had demanded lychee and longan trees to be planted in his palace gardens in Shaanxi, but the plants failed. Four hundred years later, longan trees flourished in other parts of China like Fujian and Guangdong, where longan production soon became an industry.

Later on, due to immigration and the growing demand for nostalgic foods, the longan tree was officially introduced to Australia in the mid-1800s, Thailand in the late-1800s, and Hawaii and Florida in the 1900s. The warm, sandy-soiled conditions allowed for the easy growth of longan trees. This jump-started the longan industry in these locations.

Despite its long success in China, the longan is considered to be a relatively new fruit to the world. It has only been acknowledged outside of China in the last 250 years. The first European acknowledgment of the fruit was recorded by Joao de Loureiro, a Portuguese Jesuit botanist, in 1790. The first entry resides in his collection of works, Flora Cochinchinensis.

Currently, longan crops are grown in southern China, Taiwan, northern Thailand, Malaysia, Indonesia, Cambodia, Laos, Vietnam, India, Sri Lanka, Philippines, Australia, the United States, and Mauritius. It is also grown in Bangladesh.

The fruit is highly valued in the Orient, especially in China, both as a food and as a medicine. It is often sold in local markets and is also sometimes exported. The tree is often cultivated in tropical, subtropical and frost-free warm temperate areas for its edible fruit.

The fruit is sweet, juicy, and succulent in superior agricultural varieties. The mucilaginous flesh is whitish, translucent and somewhat sweet, though not as flavoursome as the related lychee(Litchi chinensis). The seed and the peel are not consumed. Apart from being eaten raw like other fruits, longan fruit is also often used in Asian soups, snacks, desserts, and sweet-and-sour foods, either fresh or dried, and sometimes preserved and canned in syrup. The taste is different from lychees; while longan has a drier sweetness similar to dates, lychees are often messily juicy with a more tropical, grape-like sour sweetness.

Longans are much eaten fresh, out-of-hand, but some have maintained that the fruit is improved by cooking. In China, the majority are canned in syrup or dried. For drying, the fruits are first heated to shrink the flesh and facilitate peeling of the rind. Then the seeds are removed and the flesh dried over a slow fire. The dried product is black, leathery and smoky in flavour and is mainly used to prepare an infusion drunk for refreshment.

In Chinese food therapy and herbal medicine, it is believed to have an effect on relaxation.

The flesh of the fruit is administered as a stomachic, febrifuge and vermifuge, and is regarded as an antidote for poison. A decoction of the dried flesh 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 snakebite in the belief that it will absorb the venom.

Leaves and flowers are sold in Chinese herb markets but are not a 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, serves as a styptic.

The seeds, because of their saponin content, are used like soapberries (Sapindus saponaria L.) for shampooing the hair.

The seeds and the rind are burnt for fuel.

Source:
https://en.wikipedia.org/wiki/Longan
https://tropical.theferns.info/viewtropical.php?id=Dimocarpus+longan