From Plant Resources of South-East Asia No 2: Edible fruits and nuts, PROSEA Foundation
by C. M. Menzel
Taxon
Litchi chinensis Sonn.
Protologue
Voy. Indes Orient. Chine 2: 230, t. 129 (1782).
Family
SAPINDACEAE
Chromosome Numbers
2n = 28, 30 or 32
Synonyms
— ssp. chinensis: Dimocarpus litchi Lour. (1790), Litchi sinense J. Gmelin (1791), Nephelium litchi Cambess. (1829);
— ssp. philippinensis (Radlk.) Leenh.: Euphoria didyma Blanco (1837) nom. illeg., Litchi philippinensis Radlk. (1914);
— ssp. javensis Leenh.: Litchi chinensis Sonn. f. glomeriflora Radlk. (1932).
Vernacular Names
— ssp. chinensis:
Lychee, litchi (En). Cérisier de la Chine, litchi de Chine (Fr).
Indonesia: litsi (Indonesian), klèngkeng (Javanese), kalèngkeng
(Madurese). Malaysia: laici, kelengkang. Philippines: letsias. Burma:
kyet-mouk, lin chi, lam yai. Cambodia: kuléén. Laos: ngèèw. Thailand:
linchee, litchi, see raaman (Chantaburi). Vietnam: vai, cây vai, tu hú.
— ssp. philippinensis: Philippines: alupag, arupag (Tagalog), mamata (Subanum).
— ssp. javensis: Indonesia: klengkeng (Javanese), lengkeng (Sundanese), kalengkeng (Madurese).
Origin and Geographic Distribution
The
cultivated lychee originated in the region between southern China,
northern Vietnam and Malaysia. Wild trees grow in elevated and low rain
forests; in some parts of southern China lychee is one of the main
forest species. Lychee has a long history in southern China and has
undergone intensive selection. It was cultivated by people of Malayan
descent possibly as early as 1500 BC, long before the Chinese moved
that far south. The spread of lychee to other countries in the last 400
years has been slow, due to the exacting climatic requirement and the
short life of its seed. Within South-East Asia only northern Thailand
produces lychee in quantity and there is one valley in Bali where the
crop is grown commercially. Elsewhere in South-East Asia the trees
usually fail to flower, although in Thailand a lowland type lychee
bears fruit.
Uses
Lychees are cultivated for
their fruit. They have a long history of acceptance in China and many
parts of South-East Asia. Traditionally much fruit used to be traded as
'dried lychee nuts', but this form of preservation has been partly
replaced by canning. China, Taiwan and Thailand have substantial
canning industries. The present destination of the crop in China is:
60% fresh, 20% canned and 20% dried. Lychee fruit can also be processed
into juice and wine. Lychee honey is of excellent quality. The fruit,
its peel and the seed are used in traditional medicine, decoctions of
the root, bark and flowers are gargled. The timber is said to be nearly
indestructible.
Production and International Trade
The
main producing countries are Taiwan (131 000 t), India (91 860 t),
China (61 820 t), Madagascar (35 000 t), Thailand (8401 t), South
Africa (5687 t), Australia (1500 t) Mauritius (1000 t) and Reunion
(1000 t). There is also interest in the crop in Vietnam, New Zealand
and the United States. Production in southern China is centred in
Guangdong and Fujian where lychee ranks either 2nd or 3rd in importance
behind citrus and longan. Thailand and Taiwan exported about 12 000 t
of lychee to Singapore and Hong Kong in 1984. About 2000 t of fruit are
exported to Europe, mainly from South Africa, Mauritius and Reunion.
Properties
The
food value of lychee lies in its sugar content which ranges from 7—21%,
depending on climate and cultivar. Lychee fruits also contain about
0.7% protein, 0.3% fat, 0.7% minerals (particularly Ca and P) and are
reasonable sources of vitamins C (64 mg/100 g pulp), A, B1 and B2. The
strong appeal of lychee lies in the exquisite aroma of the fruit. In
the best cultivars the aril completely covers the seed and may comprise
70—80% of the fruit weight. In some cultivars a high proportion of the
seeds aborts. Fruit with these small and shrivelled seeds ('chicken
tongue' seeds) are preferred, since they contain a greater proportion
of flesh.
Description
A
large, long-lived, evergreen tree up to 30 m tall, with a short stocky
trunk; in some cultivars branches crooked or twisting, spreading,
forming a crown broader than high; in other cultivars branches fairly
straight and upright, forming a compact rounded crown. Leaves
alternate, pinnately compound, 2—4(—5)-jugate; petiolules 3—8 mm long;
leaflets oblong-lanceolate, (3—)8—11(—16) cm x 1.75—4 cm, chartaceous
to coriaceous, glossy and deep green above, glaucous beneath.
Inflorescences many-branched panicles, 5—30 cm long, many-flowered;
flowers small, yellowish-white, functionally male or female; calyx
4-merous; corolla absent; stamens 6(—10), filaments in male flowers at
least twice the length of the calyx, in female flowers very short.
Fruit a rounded, ovoid or heart-shaped drupe, ca. 3—3.5 cm in diameter;
exocarp thin, leathery, bright red to purplish, nearly smooth or scaly
to densely set with flat, conical, acute warts; the fleshy edible
portion is the aril, an outgrowth of the seed stalk, in good fruits
comprising 70—80% of the fruit weight; aril white and translucent. Seed
10—23 mm x 6—12 mm, brown.
Growth and Development
Vegetative
growth occurs as a series of flushes alternated with periods of
dormancy. Flushes last shorter periods and follow one another more
rapidly at high temperatures (25—30°C) and constant water supply. The
desirable growth rhythm is 2—3 months of vegetative growth after
harvest, followed by a rest period 1—2 months before panicle emergence
early in the cool season. Panicle and flower development continues
uninterrupted and leads to bloom 6—12 weeks after floral induction.
Fruit set — at the end of the cool season — normally lasts 4—6 weeks
for a single cultivar. Fruit is ready for harvest after 11—16 weeks,
completing the crop cycle.
Excessive vegetative growth is a serious
problem as it interferes with flowering and fruit set. Trees propagated
by air layering usually produce commercial crops after 3—6 years.
Other Botanical Information
At present, the genus Litchi Sonn. comprises only the species Litchi chinensis, which can be divided into 3 subspecies:
— ssp. chinensis:
twigs slender; leaves 2—4-jugate; flowers in lax cymules, stamens
6(—10); fruits smooth or with pyramidal warts up to 1 mm high. It is
the commonly cultivated Chinese fruit tree, probably originating from
northern Indo-China; it grows wild in northern Vietnam and Cambodia. In
China two cultivar groups are distinguished: the 'water lychee' — with
the best cultivars, cultivated in the lowlands, fruits nearly smooth,
and the 'mountain lychee' — cultivated in hilly regions, fruits smaller
and more prickly, used as a rootstock.
— ssp. philippinensis:
twigs slender; leaves 1—2(—3)-jugate; flowers in lax cymules, stamens
(6—)7; fruits with pyramidal warts up to 3 mm high. Only known from the
Philippines, where it is rather common and widely distributed, but
rarely cultivated.
— ssp. javensis:
twigs thick; leaves 2—4-jugate; flowers in sessile clusters, stamens
7—11; fruits smooth or with pyramidal warts up to 1 mm high. The plant
is only known from cultivation in West Java and southern Indo-China; it
may be suited to more humid tropical conditions.
The lychee has
undergone intensive selection: the first book on tree fruits in China
was devoted to a description of the countless lychee cultivars. The
main cultivars in southern China are 'Souey Tung', 'Haak Yip' and 'Wai
Chee', followed by 'Tai So', 'Sum Yee Hong', 'Chen Zi', 'Kwai Mai',
'Fay Zee Siu' and 'No Mai Chee'. Production in other countries is based
on Chinese cultivars: 'Haak Yip' in Taiwan, 'Tai So' and 'Wai Chee' in
Thailand (named 'Hong Huay' and 'Cheng Keng' respectively in Thailand);
'Tai So' in South Africa; and 'Tai So' and 'Bengal' (from India), 'Kwai
Mai' (Pink) and 'Wai Chee' in Australia. The only exception is India,
where local selections of Chinese imports predominate.
Ecology
The
lychee is one of the most environmentally sensitive of the tropical
tree crops. It is adapted to the tropics and warm subtropics (between
13—32°N and 6—29°S), cropping best in regions with winters that are
short, dry and cool (daily maximum below 20—22°C) but frost free, and
summers that are long and hot (daily maximum above 25°C) with high
rainfall (1200 mm) and high humidity. Good protection from wind is
essential for cropping. Year-to-year variations in weather precipitate
crop failures, e.g. through untimely rain promoting flushing at the
expense of floral development or through poor fruit set following cool
damp weather during bloom, even though mean climatic data appear
favourable for lychee.
Propagation and planting
Air
layering is the main commercial method of propagation and rates of
success are usually not less than 95%. Other methods of propagation
include grafting (useful for top-working older trees), budding and use
of cuttings (for the rapid multiplication of new cultivars).
Incompatibility occurs in some scion/rootstock combinations.
Spacing
is 6 m x 6 m (280 trees/ha) for upright cultivars such as 'Kwai Mai
Pink'. More vigorous cultivars such as 'Tai So', 'Souey Tung' and 'Haak
Yip' can be planted at 9—12 m between the rows and 6 m between trees
(140—185 trees/ha). Orchards need to be thinned out to 70 trees per ha;
the density of the closely planted orchards is halved twice at ages 10
and 15 year approximately.
Husbandry
Lychee
orchards are normally irrigated except in China. Water is withheld to
maintain shoot rest during the 2—3 months before emergence of the
inflorescences. During the remainder of the crop cycle moisture stress
should be prevented.
Fertilizer applications also should limit trees
to a single flush after harvest, maintaining subsequent shoot rest.
Thus leaf N should be kept below 1.5—1.8% before panicle emergence. To
support floral development and improve fruit retention, fertilizer is
applied at panicle emergence and after fruit set. Other times are also
mentioned in China and South Africa (before and after harvest).
Suggested amounts for well-grown 5-year-old trees are 200 g N, 80 g P
and 300 g K per year, increasing to 1000 g N, 300 g P and 1400 g K per
year at year 15. Leaf nutrient standards developed for healthy,
high-yielding trees in Australia: 1.5—1.8% for N; 0.14—0.22% for P;
0.70—1.10% for K; 0.60—1.00% for Ca; 0.30—0.50% for Mg.
Cincturing
has been used commercially in China, Thailand, Australia, Florida and
Hawaii to impose shoot rest and improve flowering and fruiting. Trees
are cinctured at the completion of the post-harvest flush, if they are
healthy and did flush actively.
The general response of lychee trees
to any form of pruning is to fill the gaps with vigorous, less fruitful
foliage as quickly as possible. Pruning is limited to the first few
years to shape the tree. Every 2—3 years older trees are skirted and
the interior is thinned after harvest by removing some of the weaker
branches completely, to improve structure against wind damage. Clipping
the panicles at harvest is a form of pruning too; if too much leaf and
wood is removed in the process, flowering in the next year can be
reduced.
Diseases and Pests
No major disease currently limits lychee growing. A parasitic alga (Cephaleuros
sp.) occasionally attacks trees causing loss of vigour. Susceptible
cultivars such as 'Souey Tung' and 'Haak Yip' can be protected with two
sprays of copper, before and after the wet season. A slow decline and a
sudden death have been recorded in southern Queensland, especially on
poorly drained soils. Three genera of nematodes (Xiphinema, Paratrichodorus and Helicotylenchus)
have been associated with tree decline in Australia. In South Africa
post-planting nematicides have shown considerable promise. Basically,
the pest complex affecting the crop is the same in different countries.
Erinose mite (Eriophyes litchii)
is the major pest of the foliage. Severe infestations may damage
developing flowers and fruit and kill the growing points. Erinose mite
can be very difficult to eradicate; dipping air layers in dimethoate
helps prevent the introduction of the mite into orchards. Red-shoulder
beetles (Monolepta australis), leaf rolling caterpillars (Platypeplus aprobola and Isotenes miserana) and scales (Chloropulvinaria psidii) occasionally attack lychee trees but can be adequately controlled. Several caterpillars (Phycita leucomilta, Lobesia spp. and Prosotas
spp.) attack developing panicles and flowers. One or two sprays of
methomyl during the season give effective control. Flowers can also be
affected by red-shoulder beetles, thrips and rutherglen bugs. The main
insects affecting fruit are fruit spotting bug (Amblypelta nitida and A. lutescens), lychee stink bug (Lyramorpha rosea or Tessaratoma papillosa in China), and a number of moth species, including fruit-piercing moths (e.g. Othreis fullonia) and borers (e.g. Acrocercops glomerella,
also found in rambutan and cacao). The bugs cause the loss of young
fruit; insecticides provide control. The moths may also cause premature
fruit drop, but the deterioration of damaged fruit after harvest is
more serious; they cannot all be adequately controlled.
Birds and flying foxes cause serious damage in Australia, Thailand and South Africa in some years.
Harvesting
Lychees
do not ripen off the tree. Maturity is judged by a particular shape,
skin colour, skin texture and flavour of each cultivar. A maturity
index based on sugar/acid ratio has been developed in Australia. Most
fruit can be picked from a tree within 1 week and from a single
cultivar in an orchard within 3 weeks. Most growers plant a range of
cultivars to spread the picking workload. April to June is the harvest
season in northern Thailand. In Bali the fruit is picked around
October; in East Kalimantan fruit from forest trees is available in
February—March. In most parts of Asia, bunched panicles of fruit are
marketed. Standard grades for detached fruits have been developed in
Australia.
Yield
Average
yields for a 10-year-old tree in southern Queensland range from about
10—50 kg/tree per year in an irregular bearing cultivar such as 'Tai
So' to 30—80 kg/tree for a regular bearing cultivar such as 'Wai Chee'.
These yields are equivalent to 0.7—11.2 t/ha per year at recommended
spacings. Yields of 10 t/ha are attained in well managed orchards in
Guangdong, but average yields are only about 2 t/ha per year.
Handling After Harvest
Lychees
in Asia are marketed in 22—25 kg bamboo baskets, normally without any
refrigeration or post-harvest treatment and consumed within 3 days of
picking. Lychees lose their bright red skin and turn brown within a few
days after harvest, especially in low humidity. High humidity tends to
encourage post-harvest rots. To prevent browning and rotting,
Australian growers dip fruit, particularly if not refrigerated on the
farm, in 0.5 g benomyl/l solution at 52°C for 2 min. Punnets with PVC
covers are used; the film retains sufficient humidity to inhibit
browning without condensation clouding the pack. Storage at 5—8°C can
prolong shelf life of treated fruit by 4—6 weeks.
Genetic Resources
Most
of the world's production is based on Chinese cultivars selected under
Chinese conditions. Consequently the genetic diversity of cultivated
lychee is narrow. Few attempts have been made to collect material of
the 3 subspecies in the wild. Collections of commercial cultivars are
held at several places in southern China and also at research
institutes in Taiwan, Thailand, India, South Africa, Australia and the
United States.
Breeding
Most
cultivars are selections from open-pollinated seedlings. The industry
in southern Thailand is based on local selections of Chinese cultivars
which crop under tropical conditions. However, fruit quality does not
match that of the Chinese cultivars. During the last 50 years a few
cultivars have been bred in Florida and Hawaii; of these only 'Kaimana'
warrants further attention. More recently there have been attempts in
Taiwan and Australia to cross-pollinate cultivars with specific
characteristics. Most breeding programmes have been limited to small
populations of 200—500 plants. Desirable characteristics: regular high
yields, large fruit size, bright red skin colour, small seed size, high
eating quality, and acceptable ripening and storage. Crosses between
the lychee and the longan in the 1920s in China yielded no exceptional
fruit.
Prospects
The
lychee is an attractive fruit with a strong appeal, traditionally
particularly in China, but nowadays also world-wide. Rapid expansion of
lychee growing takes place mainly in countries where it is still a
minor crop. However, the ultimate increase in production may not be
spectacular, as crop failures, caused by deviations from the exacting
ecological requirements, dampen the enthusiasm of the growers.
Only
when the grower has the means to impose a growth rhythm on the trees
that guarantees adequate flowering and more dependable yields, also in
years with adverse weather, can a real breakthrough of the crop be
expected. Such growing techniques (e.g. better defined application of
girdling, water and nutrients) may also widen the scope for lychee
within South-East Asia: more localities in east Indonesia could grow
cultivars of ssp. chinensis and commercial production of the other
subspecies might become feasible.
Literature
Anonymous,
1985. An album of Guangdong litchi varieties in full colour. Guangdong
Province Scientific Technology Commission. 78 pp.
Groff, G.W., 1921. The lychee and longan. Orange Judd Company, New York. 188 pp.
Menzel, C.M., 1983. The control of floral initiation in lychee: a review. Scientia Horticulturae 21: 201—215.
Menzel, C.M., 1984. The pattern and control of reproductive growth in lychee: a review. Scientia Horticulturae 22: 333—345.
Menzel,
C.M. & Simpson, D.R., 1986. Description and performance of major
lychee cultivars in subtropical Queensland. Queensland Agricultural
Journal 112: 125—136.
Menzel, C.M. & Simpson, D.R., 1987. Lychee nutrition: a review. Scientia Horticulturae 31: 195—224.
Menzel, C.M., Watson, B.J. & Simpson, D.R., 1988. The lychee in Australia. Queensland Agricultural Journal 114: 19—27.
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