Longan

This article is about the fruit and tree. For other uses, seeLong'an (disambiguation).For places in China, seeLongnanandLongyan.

Not to be confused withLoganberry.

Longan
Conservation status
Data Deficient(IUCN 3.1)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Sapindales
Family:	Sapindaceae
Genus:	Dimocarpus
Species:	D. longan
Binomial name
Dimocarpus longan Lour.
Synonyms
Dimocarpus undulatusWight Euphoria cinerea(Turcz.) Radlk. Dimocarpus leichhardtiiS.T. Reynolds Euphoria glabraBlume Euphoria gracilisRadlk. Euphoria leichhardtiiBenth. Euphoria longan(Lour.) Steud. Euphoria longanaLam. Euphoria malaiensis(Griff.) Radlk. Euphoria microcarpaRadlk. Euphoria nephelioidesRadlk. Euphoria verruculosaSalisb. Nephelium longan(Lour.) Hook. Nephelium longanaCambess.

Longan
"Longan" in Traditional (top) and Simplified (bottom) Chinese characters
Traditional Chinese	Long nhãn
Simplified Chinese	Long nhãn
Literal meaning	'dragon eye'
Transcriptions Standard Mandarin Hanyu Pinyin lóngyǎn Bopomofo ㄌㄨㄥˊ ㄧㄢˇ Wade–Giles lung2-yen3 IPA [lʊ̌ŋ.jɛ̀n] Wu Suzhounese lón-ngê Yue: Cantonese Yale Romanization lùhng-ngáahn Jyutping lung4-ngaan5 IPA [lʊŋ˩.ŋan˩˧] Southern Min HokkienPOJ lêng-géng Tâi-lô lîng-gíng

Dimocarpus longan,commonly known as thelongan(/ˈlɒŋɑːnˈ/) anddragon's eye,is a tropical tree species that produces edible fruit.It is one of the better-known tropical members of the soapberry familySapindaceae,to which thelycheeandrambutanalso belong.The fruit of the longan is similar to that of the lychee, but is less aromatic in taste.

The longan (fromVietnameselong nhãn,close toCantoneselùhng ngáahnLong nhãn,literally 'dragon eye'), is so named because the black seed within the shelled fruit creates the appearance of an eyeball. The plant is native to tropical Asia and China.

Description

Depending upon climate and soil type the tree may grow to over 30 metres (100 ft)in height, but it typically stands 9–12 m (30–40 ft) in height and thecrownis round.The trunk is80 cm (2+1⁄2ft) thickwith corkybark.The branches are long and thick, typically drooping.

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

The longan tree produces light-yellowinflorescencesat the end of branches.The inflorescence is commonly called apanicle;they can be 10–46 cm (4–18 in) long, and widely branched.The smallflowershave 5 to 6sepalsandpetalsthat are brownish-yellow.The flower has a two-lobedpistiland 8stamen.There are three flower types, distributed throughout the panicle;staminate (functionally male), pistillate (functionally female), andhermaphroditicflowers.Flowering occurs as a progression.

The fruit are circular and about 2.5 cm (1 in) wide; they hang in drooping clusters. The shell is tan, thin, and leathery with tiny hairs;when firm, it can be squeezed (as in the cracking of asunflower seed) to shell the fruit.The flesh is translucent, and theseedis 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 oflycheefruit.The seed is round, hard, and has a lacquered appearance.

The longan tree is somewhat sensitive tofrost.Longan trees prefer sandy soil. While the species prefers temperatures that do not typically fall below 4.5 °C (40 °F), it can withstand brief temperature drops to about −2 °C (28 °F).Longan trees prefer sandy soil with mild levels of acidity andorganic matter.Longans usually bear fruit slightly later than lychees.

• 
  Lower trunk
• 
  Tree leaves
• 
  Branch of baby fruits
• 
  Bunch of fruit
• 
  Fruit with flesh, seed, and peel visible
• Longan being peeled and eaten

Taxonomy

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

Its earliest record of existence draws back to theHan dynastyin 200BCE.The emperor had demanded lychee and longan trees to be planted in his palace gardens inShaanxi,but the plants failed. Four hundred years later, longan trees flourished in other parts of China likeFujianandGuangdong,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 byJoão de Loureiro,a Portuguese Jesuit botanist, in 1790. The first entry resides in his collection of works,Flora Cochinchinensis.

Subspecies

Plants of the World Onlinelists:

• D. longanvar.echinatusLeenhouts (Borneo, Philippines)
• D. longanvar.longetiolatusLeenhouts (Viet Nam)
• D. longansubsp.malesianusLeenh. (widespread SE Asia)
• D. longanvar.obtusus(Pierre) Leenh. (Indo-China)

Conservation

The wild longan population have been decimated considerably by large-scale logging in the past, and the species used to be listed asVulnerableon theIUCN Red List.If left alone, longan tree stumps will resprout and the listing was upgraded toNear Threatenedin 1998. Recent field data are inadequate for a contemporary IUCN assessment.

Diseases

Plant based diseases can affect both longan fruits and their trees, and the severity of these diseases can range from harmless cosmetic damage to rendering to the fruit inedible.

The most prevalent disease among longan plants iswitch's broom,which can be found in all major longan-producing Asian territories, including China, Thailand, and Vietnam.Witch's broom deforms longan skin, and at times causes the plant to prematurely drop its fruit, similar to thePhytophthora palmivora.

Another common disease that longan trees can carry is the aptly namedlongan decline,which is largely prevalent in Thailand, with reports finding that it could affect up to 40% of longan trees alone.Affected trees are more vulnerable to common tree pests and algae, and often bear low-quality fruit unworthy of yield.

Algal spotis another plant disease that can affect longan plants and trees. Common among tropical fruits, the disease mainly takes form as red-orange algae that can appear on a fruit-bearing tree's leaves or branches.Algal spoton longan plants, like many other tropical fruits, is caused byCephaleuros virescens.

An oomycete disease that causesblighton leaves and foliage of a plant and affects the related lychee,Phytophthora palmivora,can also appear on both longan plants and fruit,particularly in the Thailand region. When affecting longan, it can create brown spots on the fruit in an erratic fashion, and can also cause longan to drop prematurely from the plant. Early symptoms can also include a darknecrosison the plant itself.

Stem-end rot is a disease common amongst litchi and longan, and causes browning and rot on the stem of the fruit. Longan also suffer from various decay-accelerating fungi.

An oomycete disease that affects the related lychee,Phytophthora litchii,also afflictsD. longan.

Cultivation

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

Growth

Longan, like its sister fruit lychee, thrives in humid areas or places with high rainfall, and can grow on most types of soil that does not induce issues with water drainage.Ample temperatures are also instrumental in longan growth: while longan can resist small stretches of cool temperatures, they can be damaged or killed in longer stretches of temperatures as high as −2 degrees Celsius. Younger plants tend to be more vulnerable to the cold than those more mature.

Longans, raw

A peeled longan fruit
Nutritional value per 100 g (3.5 oz)
Energy	251 kJ (60 kcal)
Carbohydrates	15.14 g
Sugars	n/a
Dietary fiber	1.1 g
Fat	0.1 g
Protein	1.31 g
Threonine	0.034 g
Isoleucine	0.026 g
Leucine	0.054 g
Lysine	0.046 g
Methionine	0.013 g
Phenylalanine	0.030 g
Tyrosine	0.025 g
Valine	0.058 g
Arginine	0.035 g
Histidine	0.012 g
Alanine	0.157 g
Aspartic acid	0.126 g
Glutamic acid	0.209 g
Glycine	0.042 g
Proline	0.042 g
Serine	0.048 g
Vitamins and minerals Vitamins Quantity %DV† Thiamine (B1) 3% 0.031 mg Riboflavin (B2) 11% 0.14 mg Niacin (B3) 2% 0.3 mg Vitamin C 93% 84 mg Minerals Quantity %DV† Calcium 0% 1 mg Iron 1% 0.13 mg Magnesium 2% 10 mg Manganese 2% 0.052 mg Phosphorus 2% 21 mg Potassium 9% 266 mg Sodium 0% 0 mg Zinc 0% 0.05 mg
Other constituents	Quantity
Water	83 g
Link to USDA Database entry
†Percentages estimated usingUS recommendationsfor adults,except for potassium, which is estimated based on expert recommendation fromthe National Academies.

Harvest

During harvest, pickers must climb ladders to carefully remove branches of fruit from longan trees. Longan fruit remain fresher if still attached to the branch, so efforts are made to prevent the fruit from detaching too early. Mechanical picking would damage the delicate skin of the fruit, so the preferred method is to harvest by hand. Knives and scissors are the most commonly used tools.

Fruit is picked early in the day to minimize water loss and to prevent high heat exposure, which would be damaging. The fruit is then placed into either plastic crates or bamboo baskets and taken to packaging houses, where the fruit undergo a series of checks for quality. The packaging houses are well-ventilated and shaded to prevent further decay. The process of checking and sorting are performed by workers instead of machinery. Any fruit that is split, under-ripe, or decaying is disposed of. The remaining healthy fruit is then prepared and shipped to markets.

Many companies add preservatives to canned longan. Regulations control the preserving process. The only known preservative added to canned longan issulfur dioxide,to prevent discoloration.Fresh longan that is shipped worldwide is exposed to sulfurfumigation.Tests have shown that sulfur residues remain on the fruit skin, branches, and leaves for a few weeks. This violates many countries' limits on fumigation residue, and efforts have been made to reduce this amount.

Distribution

Longan is found commonly in most of Asia, primarily in mainland China, Taiwan, Vietnam and Thailand. China, the main longan-producing country in the world, produced about 1.9 million metric tons (2.1 million short tons) of longan in 2015–2017, accounting for 70% of the world's longan production and more than 50% of the world's longan plots.Vietnam and Thailand produced around 500 and 980 thousand metric tons (550 and 1,080 thousand short tons), respectively.Like Vietnam, Thailand's economy relies heavily on the cultivation and shipments of longan as well as lychee. This increase in the production of longan reflects recent interest in exotic fruits in other parts of the world. However, the majority of the demand comes from Asian communities in North America, Europe and Australia.

Yield

While longan yields average out to 2 to 5 tonnes per hectare, there have been observed yields of up to 19.5 tonnes per ha inIsrael.

Advancements inselective breedinghave allowed scientists to find a strain of longan containing a "high proportion of aborted seeds" at the end of a thirty-year breeding program in 2001.Studies in 2015 that aimed to aid longan breeding efforts discovered that −20 degrees Celsius is the optimal temperature for long-term storage of longan pollen, a key ingredient in enabling longan breeding programs.

Uses

Nutrition

Raw longan fruit is 83% water, 15%carbohydrates,1%protein,and contains negligible fat. In a 100 gram reference amount, raw longan supplies 60caloriesof food energy, 101% of theDaily Value(DV) ofvitamin C,12% DV ofriboflavin,and no othermicronutrientsin appreciable quantities.

Culinary

The fruit is sweet, juicy, and succulent in superior agricultural varieties. 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, andsweet-and-sourfoods, 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.

Dried longan are often used inChinese cuisineand Chinese sweet dessert soups. InChinese food therapyandherbal medicine,it is believed to have an effect on relaxation.In contrast with the fresh fruit, which is juicy and white, the flesh of dried longans is dark brown to almost black.

Once fermented, it can be made intolongan wine.

See also

• Lansium parasiticum,the langsat or lanzones
• Talisia esculenta,a visually similar fruit from South America

External links

• Longan Production in Asiafrom theFood and Agriculture Organizationof the United Nations