Longan

Plants of the World Online[6] lists:

• D. longan var. echinatus Leenhouts (Borneo, Philippines)
• D. longan var. longetiolatus Leenhouts (Viet Nam)
• D. longan subsp. malesianus Leenh. (widespread SE Asia)
• D. longan var. obtusus (Pierre) Leenh. (Indo-China)

Longan fruit with flesh, seed, and peel visible.

Depending upon climate and soil type the tree may grow to over 100 feet (30 m)[7] in height, but it typically stands 30–40 ft (9–12 m) in height and the crown is round.[3][8] The trunk is 2.5 ft (0.8 m) thick[3] with corky bark.[8] The branches are long and thick, typically drooping.[3]

The leaves are oblong and blunt-tipped, usually 4–8 inches (10–20 cm) long and 2 in (5 cm) wide.[3] The leaves are pinnately compounded and alternate.[8] There are 6 to 9 pairs of leaflets per leaf[8] and the upper surface is wavy and a dark, glossy-green.[3]

The longan tree produces light-yellow inflorescences at the end of branches.[3] The inflorescence is commonly called a panicle and are 4–18 in (10–46 cm) long, and widely branched.[8] The small flowers have 5 to 6 sepals and petals that are brownish-yellow.[8] The flower has a two-lobed pistil and 8 stamen. There are three flower types, distributed throughout the panicle;[3] staminate (functionally male), pistillate (functionally female), and hermaphroditic flowers.[8] Flowering occurs as a progression.[8]

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.[8] The flesh is translucent, and the seed is large and black with a circular white spot at the base.[3][8] This gives the illusion of an eye.[3] The flesh has a musky, sweet taste, which can be compared to the flavor of lychee fruit.[3]

The longan tree is somewhat sensitive to frost. 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).[9] Longan trees prefer sandy soil with mild levels of acidity and organic matter.[3] Longans usually bear fruit slightly later than lychees.[10]

The wild longan population have been decimated considerably by large-scale logging in the past, and the species used to be listed as Vulnerable on the IUCN Red List. If left alone, longan tree stumps will resprout and the listing was upgraded to Near Threatened in 1998. Recent field data are inadequate for a contemporary IUCN assessment.[1]

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.[11]

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.[12]

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.[12]

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.[12] 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.[4]

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.[11] It is also grown in Bangladesh.[13]

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	Quantity %DV†
Thiamine (B1)	3% 0.031 mg
Riboflavin (B2)	12% 0.14 mg
Niacin (B3)	2% 0.3 mg
Vitamin C	101% 84 mg
Minerals	Quantity %DV†
Calcium	0% 1 mg
Iron	1% 0.13 mg
Magnesium	3% 10 mg
Manganese	2% 0.052 mg
Phosphorus	3% 21 mg
Potassium	6% 266 mg
Sodium	0% 0 mg
Zinc	1% 0.05 mg
Other constituents	Quantity
Water	83 g
Link to USDA Database entry
Units μg = micrograms • mg = milligrams IU = International units
†Percentages are roughly approximated using US recommendations for adults. Source: USDA FoodData Central

Raw longan fruit is 83% water, 15% carbohydrates, 1% protein, and contains negligible fat. In a 100 gram reference amount, raw longan supplies 60 calories of food energy, 101% of the Daily Value (DV) of vitamin C, 12% DV of riboflavin, and no other micronutrients in appreciable quantities.

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 is the Witch's broom, which can be found in all major longan-producing Asian territories, including China, Thailand, and Vietnam.[27] Witch's Broom works on deforming longan skin, and at times having the plant prematurely drop their fruit, similar to the Phytophthora palmivora.[28]

Another common disease that longan trees can carry is the aptly named Longan Decline, which is largely prevalent in Thailand, with reports finding that it could affect up to 40% of longan trees alone.[29] Affected trees are more vulnerable to common tree pests and algae, and often bear low-quality fruit unworthy of yield.[29]

Algal spot is 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.[30]Algal spot on longan plants, like many other tropical fruits, is caused by Cephaleuros virescens.[31]

An oomycete disease that causes blight on leaves and foliage of a plant and affects the related lychee, Phytophthora palmivora, can also appear on both longan plants and fruit,[32] 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 dark necrosis on the plant itself.[33]

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.[29]

An oomycete disease that affects the related lychee - Phytophthora litchii - also afflicts D. longan.[32]

• 
  Longan (Dimocarpus longan) tree leaves
• 
  Longan tree lower trunk
• 
  The longan was described in Joao de Loureiro's work, Flora Cochinchinensis, published in 1790
• 
  Longan (Dimocarpus longan) baby fruits and leaves

• Lansium parasiticum, the langsat or lanzones

• Longan Production in Asia from the Food and Agriculture Organization of the United Nations

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