From the book
Fruits of Warm Climates
by Julia F. Morton
Longan
Dimocarpus
longan Lour.
Euphoria longan Steud.
Euphoria longana Lam.
Nephelium longana Cambess.
SAPINDACEAE
Closely allied to the glamorous lychee, in the family Sapindaceae, the
longan, or lungan, also known as dragon's eye or eyeball, and as
mamoncillo chino in Cuba, has been referred to as the "little brother
of the lychee", or li-chihnu, "slave of the lychee". Botanically, it is
placed in a separate genus, and is currently designated Dimocarpus longan
Lour. (syns. Euphoria
longan Steud.; E.
longana Lam.; Nephelium
longana
Cambess.). According to the esteemed scholar, Prof. G. Weidman Groff,
the longan is less important to the Chinese as an edible fruit, more
widely used than the lychee in Oriental medicine.
Description
The
longan tree is handsome, erect, to 30 or 40 ft (9-12 m) in height and
to 45 ft (14 m) in width, with rough-barked trunk to 2 1/2 ft (76.2 cm)
thick and long, spreading, slightly drooping, heavily foliaged
branches. The evergreen, alternate, paripinnate leaves have 4 to 10
opposite leaflets, elliptic, ovate-oblong or lanceolate, blunt-tipped;
4 to 8 in (10-20 cm) long and 1 3/8 to 2 in (3.5-5 cm) wide; leathery,
wavy, glossy-green on the upper surface, minutely hairy and
grayish-green beneath. New growth is wine-colored and showy. The
pale-yellow, 5- to 6-petalled, hairy-stalked flowers, larger than those
of the lychee, are borne in upright terminal panicles, male and female
mingled. The fruits, in drooping clusters, are globose, 1/2 to 1 in
(1.25-2.5 cm) in diameter, with thin, brittle, yellow-brown to light
reddish-brown rind, more or less rough (pebbled), the protuberances
much less prominent than those of the lychee. The flesh (aril) is
mucilaginous, whitish, translucent, somewhat musky, sweet, but not as
sweet as that of the lychee and with less "bouquet". The seed is round,
jet-black, shining, with a circular white spot at the base, giving it
the aspect of an eye.
Origin and
Distribution
The
longan is native to southern China, in the provinces of Kwangtung,
Kwangsi, Schezwan and Fukien, between elevations of 500 and 1,500 ft
(150-450 m). Groff wrote: "The lungan, not so highly prized as the
lychee, is nevertheless usually found contiguous to it .... It thrives
much better on higher ground than the lychee and endures more frost. It
is rarely found growing along the dykes of streams as is the lychee but
does especially well on high ground near ponds .... The lungan is more
seldom grown under orchard conditions than is the lychee. There is not
so large a demand for the fruit and the trees therefore more scattered
although one often finds attractive groups of lungan." Groff says that
the longan was introduced into India in 1798 but, in Indian literature,
it is averred that the longan is native not only to China but also to
southwestern India and the forests of upper Assam and the Garo hills,
and is cultivated in Bengal and elsewhere as an ornamental and shade
tree. It is commonly grown in former Indochina (Thailand, Cambodia,
Laos and Vietnam and in Taiwan). The tree grows but does not fruit in
Malaya and the Philippines. There are many of the trees in
Reúnion and Mauritius.
The longan was introduced into
Florida from southern China by the United States Department of
Agriculture in 1903 and has flourished in a few locations but never
became popular. There was a young tree growing at the Agricultural
Station in Bermuda in 1913. A tree planted at the Federal Experiment
Station in Mayaguez, Puerto Rico, was 10 ft (3 m) high in 1926, 23 ft
(7 m) in 1929. A longan tree flourished in the Atkins Garden in Cuba
and seedlings were distributed but found to fruit irregularly and came
to be valued mostly for their shade and ornamental quality. In Hawaii,
the longan was found to grow faster and more vigorously than the lychee
but the fruit is regarded there as less flavorful than the lychee.
Fig. 74: The brown-skinned longan (Euphoria
longan), less luscious than the lychee, is hardier, bears
heavily and later in the year.
Varieties
It
seems that the type of longan originally brought to the New World was
not one of the best, having aroused so little interest in the fruit.
Groff stated that the leading variety of Fukien was the round-fruited
'Shih hsía', the "Stone Gorge Lungan" from P'ing Chou. There
were 2 types, one, 'Hei ho shih hsia', black-seeded, and 'Chin ch' i ho
shih hsia', brown-seeded. This variety did not excel in size but the
flesh was crisp, sweeter than in other varieties, the seed small and
the dried flesh, after soaking in water, was restored almost to fresh
condition.
None of the other 4 varieties described by Groff has any great merit.
'Wu Yuan'
("black ball") has small, sour fruit used for canning. The tree is
vigorous and seedlings are valued as rootstocks.
'Kao Yuan'
is believed to be a slightly better type of this variety and is widely
canned.
'Tsao ho'
('Early Rice') is the earliest variety and a form called 'Ch'i chin
tsao ho' precedes it by 2 weeks. In quality, both are inferior to 'Wu
Yuan'.
'She p' i'
('Snake skin') has the largest fruit, as big as a small lychee and
slightly elongated. The skin is rough, the seed large, some of the
juice is between the rind and the flesh, and the quality is low. Its
only advantage is that it is very late in season.
'Hua Kioh'
('Flower Skin'), slightly elongated, has thin, nearly tasteless flesh,
some of the juice is between the rind and the flesh, and the overall
quality is poor. It is seldom propagated vegetatively.
There are no "chicken- tongue" (aborted seed) varieties in China.
There are 2 improved cultivars grown extensively in Taiwan–'Fukien Lungan'
('Fukugan') was introduced from Fukien Province in mainland China. The
other, very similar and possibly a mutant of 'Fukien', is 'Lungan Late', which
matures a month later than 'Fukien'.
In 1954, William Whitman of Miami introduced a superior variety of
longan, the 'Kohala',
from Hawaii. It began to bear in 1958. The fruit is large for the
species, the seed is small, and the flesh is aromatic, sweet and spicy.
The tree produces fairly good crops in midsummer. One hundred or more
air-layers have been brought by air from Hawaii and planted at various
locations in southern Florida and in the Bahamas. A seedling planting
and selection program was started in 1962 at the USDA Subtropical
Horticulture Research Unit, Miami. The plants were all open-pollinated
seedlings of the canning variety, 'Wu Yuan', brought in from Canton in
1930 as P.I. #89409. Some set fruit in 1966 and 1967 but more of them
in 1968. Evaluation of these and other acquisitions continues. Included
in the study are M-17886, 'Chom Poo Nuch', and M-17887, 'E-Haw'.
Climate
Professor
Groff wrote that "the lungan . . . is found growing at higher latitudes
and higher altitudes than the lychee." Also: "On the higher elevations
of the mountainous regions which are subject to frost the lychee is
seldom grown. The longan appears in these regions more often but it,
too, cannot stand heavy frosts." The longan's range in Florida extends
north to Tampa on the west coast and to Merritt Island on the east
coast. Still, small trees suffer leaf-and twig-damage if the
temperature falls to 31º or 30º F (-0.56º--l.11º C)
and are killed at just a few degrees lower. Larger trees show leaf
injury at 27º to 28º F (-2.78º--2.22º C), small
branch injury at 25º to 26º F (-3-89º--3.33º C),
large branch and trunk symptoms at 24º F (-4.44º C) and
sometimes fail to recover.
On the other hand, after a long
period of cool weather over the 3 winter months, with no frost, longan
trees bloom well. Blooming is poor after a warm winter.
Soil
The
longan thrives best on a rich sandy loam and nearly as well on
moderately acid, somewhat organic, sand. It also grows to a large size
and bears heavily in oolitic limestone. In organic muck soils, blooming
and fruiting are deficient.
Propagation
Most
longan trees have been grown from seed. The seeds lose viability
quickly. After drying in the shade for 4 day, they should be planted
without delay, but no more than 3/4 in (2 cm) deep, otherwise they may
send up more than one sprout. Germination takes place within a week or
10 days. The seedlings are transplanted to shaded nursery rows the
following spring and set in the field 2-3 years later during winter
dormancy.
In Kwangtung Province, when vegetative propagation is
undertaken, it is mostly by means of inarching, nearly always onto 'Wu
Yuan' trees 3-5 years old and 5 to 6 ft (1.5-1.8 m) high. The union is
made no less than 4 ft (1.2 m) from the ground because it is most
convenient. Nevertheless, the point of attachment remains weak and
needs to be braced with bamboo to avoid breaking in high winds.
Grafting
is uncommon and when it is done, it is a sandwich graft on longan
rootstock, 3 or 4 grafts being made successively, one onto the beheaded
top of the preceding one, in the belief that it makes the graft
wind-resistant and that it induces better size and quality in the fruit.
Conventional
modes of grafting have not been successful in Florida, but
whip-grafting has given 80% success in Taiwan. Air-layering is
frequently done in Fukien Province and was found a feasible means of
distributing the 'Kohala' from Hawaii. Air-layers bear in 2 to 3 years
after planting. A tree can be converted to a preferred cultivar by
cutting it drastically back and veneer-grafting the new shoots.
Culture
In
China, if the longan is raised on the lowlands it is always put on the
edges of raised beds. On high ground, the trees are placed in
pre-enriched holes on the surface. The trees are fertilized after the
fruit harvest and during the blooming season, at which time the
proportion of nitrogen is reduced. Fresh, rich soil is added around the
base of the trees year after year. The longan needs an adequate supply
of water and can even stand brief flooding, but not prolonged drought.
Irrigation is necessary in dry periods.
An important operation
is the pruning of many flower-bearing twigs, 3/4 of the flower spikes
in the cluster being removed. Later, the fruit clusters are also
thinned, in order to increase the size and quality of the fruits.
Generally,
the trees are planted too close together, seriously inhibiting
productivity when they become overcrowded. In China, full-grown trees
given sufficient room–at least 40 ft (12 m) apart–may yield
400 to 500 lbs (180-225 kg) in good years. Crops in Florida from trees
20 ft (6 m) tall and broad, have varied from light–50-100 lbs
(22.5-45 kg)–to medium–150-250 lbs (68-113 kg), and
heavy–300-500 lbs (135-225 kg). Rarely such trees may produce
600-700 lbs (272-317 kg). Larger trees have larger crops but if the
trees become too tall harvesting is too difficult, and they should be
topped. Harvesters, working manually from ladders, or using pruning
poles cut the entire cluster of fruit with leaves attached.
A
serious problem with the longan is its irregular bearing–often
one good year followed by 1 or 2 poor years. Another handicap is the
ripening season–early to mid-August in China, which is the time
of typhoons; August and September in Florida which is during the
hurricane season. Rain is a major nuisance in harvesting and in
conveying the fruit to market or to drying sheds or processing plants.
Keeping
Quality
At
room temperature, longans remain in good condition for several days.
Because of the firmer rind, the fruit is less perishable than the
lychee.
Preliminary tests in Florida indicate that the fruit can be frozen and
will not break down as quickly as the lychee when thawed.
Pests and
Diseases
The
longan is relatively free of pests and diseases. At times, there may be
signs of mineral deficiency which can be readily corrected by supplying
minor elements in the fertilization program.
Food Uses
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
sirup or dried. The canned fruits were regularly shipped from Shanghai
to the United States in the past. Today, they are exported from Hong
Kong and Taiwan.
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 flavor and is mainly used to prepare an
infusion drunk for refreshment.
A liqueur is made by macerating the longan flesh in alcohol.
| Food
Value Per
100 g of Edible Portion |
|
Fresh |
Dried |
| Calories |
61 |
286 |
| Moisture |
82.4 g |
17.6 g |
| Protein |
1.0 g |
4.9 g |
| Fat |
0.1 g |
0.4 g |
| Carbohydrates |
15.8 g |
74.0 g |
| Fiber |
0.4 g |
2.0 g |
| Ash |
0.7 g |
3.1 g |
| Calcium |
10 mg |
45 mg |
| Phosphorus |
42 mg |
196 mg |
| Iron |
1.2 mg |
5.4 mg |
| Thiamine |
|
0.04 mg |
| Ascorbic Acid |
6 mg (possibly) |
28 mg |
|
Other Uses
Seeds and rind:
The seeds, because of their saponin content, are used like soapberries
(Sapindus saponaria
L.) for shampooing the hair. The seeds and the rind
are burned for fuel and are part of the payment of the Chinese women
who attend to the drying operation.
Wood:
While the tree is not often cut for timber, the wood is used for posts,
agricultural implements, furniture and construction. The heartwood is
red, hard, and takes a fine polish. It is not highly valued for fuel.
Medicinal Uses:
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. Burkill says that the dried flowers
are exported to Malaysia for medicinal purposes. The seeds are
administered to counteract heavy sweating and the pulverized kernel,
which contains saponin, tannin and fat, serves as a styptic.
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