It is a tropical tree native to the Guangdong and Fujian provinces of southeastern China, where cultivation is documented from the 11th century. China is the main producer of lychees, followed by India, other countries in Southeast Asia, the Indian Subcontinent and South Africa. A tall evergreen tree, the lychee bears small fleshy fruits. The outside of the fruit is pink-red, roughly textured and inedible, covering sweet flesh eaten in many different dessert dishes.
Lychee seeds contain methylene cyclopropyl glycine which can cause hypoglycemia associated with outbreaks of encephalopathy in undernourished Indian and Vietnamese children who had consumed lychee fruit.
Litchi chinensis is the sole member of the genus Litchi in the soapberry family, Sapindaceae. It was described and named by French naturalist Pierre Sonnerat in his account "Voyage aux Indes orientales et à la Chine, fait depuis 1774 jusqu'à 1781" (translation: "Voyage to the East Indies and China, made between 1774 and 1781"), which was published in 1782. There are three subspecies, determined by flower arrangement, twig thickness, fruit, and number of stamens.
Litchi chinensis is an evergreen tree that is frequently less than 15 m (49 ft) tall, sometimes reaching 28 m (92 ft).
Its evergreen leaves, 5 to 8 in (12.5-20 cm) long, are pinnate, having 4 to 8 alternate, elliptic-oblong to lanceolate, abruptly pointed, leaflets,
The bark is grey-black, the branches a brownish-red. Its evergreen leaves are 12.5 to 20 cm (4.9 to 7.9 in) long, with leaflets in two to four pairs. Lychee are similar in foliage to the family Lauraceae, likely due to convergent evolution. They are adapted by developing leaves that repel water, and are called laurophyll or lauroid leaves. Flowers grow on a terminal inflorescence with many panicles on the current season's growth. The panicles grow in clusters of ten or more, reaching 10 to 40 cm (3.9 to 15.7 in) or longer, holding hundreds of small white, yellow, or green flowers that are distinctively fragrant.
The lychee bears fleshy fruits that mature in 80-112 days depending on climate, location, and cultivar. Fruits vary in shape from round to ovoid to heart-shaped, up to 5 cm long and 4 cm wide (2.0 in × 1.6 in), weighing approximately 20 g. The thin, tough skin is green when immature, ripening to red or pink-red, and is smooth or covered with small sharp protuberances roughly textured. The rind is inedible but easily removed to expose a layer of translucent white fleshy aril with a floral smell and a fragrant, sweet flavor. The skin turns brown and dry when left out after harvesting. The fleshy, edible portion of the fruit is an aril, surrounding one dark brown inedible seed that is 1 to 3.3 cm long and 0.6 to 1.2 cm wide (0.39-1.30 by 0.24-0.47 in). Some cultivars produce a high percentage of fruits with shriveled aborted seeds known as 'chicken tongues'. These fruit typically have a higher price, due to having more edible flesh. Since the perfume-like flavour is lost in the process of canning, the fruit is usually eaten fresh.
Cultivation of lychee began in the region of southern China, going back to 1059 AD, Malaysia, and northern Vietnam. Unofficial records in China refer to lychee as far back as 2000 BC. Wild trees still grow in parts of southern China and on Hainan Island. The fruit was used as a delicacy in the Chinese Imperial Court. It was first described and introduced to the West in 1656 by Michal Boym, a Polish Jesuit missionary (at that time Polish-Lithuanian Commonwealth).
In the 1st century, fresh lychees were in such demand at the Imperial Court that a special courier service with fast horses would bring the fresh fruit from Guangdong. There was great demand for lychee in the Song Dynasty (960-1279), according to Cai Xiang, in his Li chi pu (Treatise on Lychees). It was also the favourite fruit of Emperor Li Longji (Xuanzong)'s favoured concubine Yang Yuhuan (Yang Guifei). The emperor had the fruit delivered at great expense to the capital.
The lychee attracted attention of European travellers, such as Juan González de Mendoza in his History of the great and mighty kingdom of China (1585; English translation 1588), based on the reports of Spanish friars who had visited China in the 1570s gave the fruit high praise:
[T]hey haue a kinde of plummes, that they doo call lechias, that are of an exceeding gallant tast, and neuer hurteth any body, although they shoulde eate a great number of them.
Lychees are extensively grown in China, India, Thailand, Vietnam and the rest of tropical Southeast Asia, the Indian Subcontinent, and in South Africa, Brazil, the Caribbean, Australia, Israel, and the southeastern United States. They require a tropical climate that is frost-free and is not below the temperature of -4 °C (25 °F). Lychees also require a climate with high summer heat, rainfall, and humidity. Growth is best on well-drained, slightly acidic soils rich in organic matter and mulch. A wide range of cultivars are available, with early and late maturing forms suited to warmer and cooler climates, respectively. They are also grown as an ornamental tree, as well as for their fruit. The most common way of propagating lychee is through a method called Air Layering or Marcotting. Air-layers, or marcotts, are made by cincturing a branch of a mature tree, covering the cut with a rooting medium, such as peat or sphagnum moss, then wrapping the medium with polyethylene film and allowing the cut to root. Once significant rooting has occurred the marcott is cut from the branch and potted up.
According to folklore, a lychee tree that is not producing much fruit can be girdled, leading to more fruit production. When the central opening of trees is carried out as part of training and pruning, stereo fruiting can be achieved for higher orchard productivity.
Lychees are commonly sold fresh in Asian markets. The red rind turns dark brown when the fruit is refrigerated, but the taste is not affected. It is also sold canned year-round. The fruit can be dried with the rind intact, at which point the flesh shrinks and darkens.
There are numerous lychee cultivars, with considerable confusion regarding their naming and identification. The same cultivar grown in different climates can produce very different fruit. Cultivars can also have different synonyms in various parts of the world. Southeast Asian countries, along with Australia, use the original Chinese names for the main cultivars. India grows more than a dozen different cultivars. South Africa grows mainly the "Mauritius" cultivar. Most cultivars grown in the United States were imported from China, except for the "Groff", which was developed in the state of Hawaii.
Different cultivars of lychee are popular in the varying growing regions and countries. In China, popular cultivars include: Sanyuehong, Baitangying, Baila, Shuidong, Feizixiao, Dazou, Heiye, Nuomici, Guiwei, Huaizhi, Lanzhu, and Chenzi. In Vietnam, the most popular cultivar is Vai thieu Hai Duong. In the US, production is based on several cultivars, including Mauritius, Brewster, and Hak Ip. India grows more than a dozen named cultivars, including Shahi (Highest Pulp %), Dehra Dun, Early Large Red, Kalkattia, Rose Scented.
Raw lychee fruit is 82% water, 17% carbohydrates, 1% protein, and contains negligible fat (table). The raw pulp is rich in vitamin C, having 72 mg per 100 grams – an amount representing 86% of the Daily Value – but contains no other micronutrients in significant content (table).
Lychees have moderate amounts of polyphenols, including flavan-3-ol monomers and dimers as major compounds representing about 87% of total polyphenols, which declined in content during storage or browning. Lychees naturally produce butylated hydroxytoluene (BHT).Cyanidin-3-glucoside represented 92% of total anthocyanins.
In 1962, it was found that lychee seeds contained methylenecyclopropylglycine (MCPG), a homologue of hypoglycin A, which caused hypoglycemia in animal studies. Since the end of the 1990s, unexplained outbreaks of encephalopathy occurred, appearing to affect only children in India (where it is called chamki bukhar), and northern Vietnam (where it was called Ac Mong encephalitis after the Vietnamese word for nightmare) during the lychee harvest season from May to June.
A 2013 investigation by the U.S. Centers for Disease Control and Prevention (CDC), in India, showed that cases were linked to the consumption of lychee fruit, causing a noninflammatory encephalopathy that mimicked symptoms of Jamaican vomiting sickness. Because low blood sugar (hypoglycemia) of less than 70 mg/dL in the undernourished children on admission was common, and associated with a poorer outcome (44% of all cases were fatal) the CDC identified the illness as a hypoglycemic encephalopathy.
The investigation linked the illness to hypoglycin A and MCPG toxicity, and to malnourished children eating lychees (particularly unripe ones) on an empty stomach. Other assessment indicated that lychee contains "unusual amino acids" affecting gluconeogenesis and ?-oxidation of fatty acids, contributing to acute illness.
Earlier studies had incorrectly concluded that transmission may occur from direct contact with lychees contaminated by bat saliva, urine, or guano or with other vectors, such as insects found in lychee trees or sand flies, as in the case of Chandipura virus. A 2017 study found that pesticides used in the plantations could be responsible for the encephalitis and deaths of young children in Bangladesh.