From Plant
Resources of South-East Asia (PROSEA)
by D.L. Schuiling,and J. P. Mogea
Taxon
Salacca zalacca (Gaertner) Voss
Protologue
Vilmorin's Blumengärtnerei ed. 3, 1: 1152 (1895).
Family
Palmae
Chromosome
Numbers
2n= 28
Synonyms
Salacca edulis Reinw. (1825).
Vernacular
Names
Salak (palm), snake fruit (En).; Indonesia and Malaysia: salak; Burma: yingan; Thailand: sala.
Origin and
Geographic Distribution
Salak
grows wild in south-western Java and southern Sumatra, but its precise
place of origin is not known. It is cultivated in Thailand, throughout
Malaysia and Indonesia as far as the Moluccas, and has been introduced
into New Guinea, the Philippines, Queensland (Australia), Ponape Island
(Caroline Archipelago) and reportedly occurs on the Fiji Islands.
Uses
Salak palm is cultivated for
its fruits, the bulk of which are consumed fresh when fully ripe. In
Indonesia the fruits are also candied ("manisan salak"), pickled
("asinan salak") and fresh unripe ones may be used in "rujak", a spicy
salad of unripe fruit. Mature fruits may be canned. The seed kernels of
the young fruits of the Javanese "Pondoh" form are edible. A
closely-planted row of palms forms an impregnable hedge and the very
spiny leaves are also cut to construct fences; the leaflets are used
for thatching. The bark of the petioles may be used for matting.
Production and international trade
Data on production and cultivated area are scarce and variable.
Production figures for Java range from 7000-50 000 t in the 1980s,
about half the crop being produced in western Java. In Indonesia, where
salak is exclusively a smallholder crop, only a tiny fraction of total
production is exported, fresh, canned or candied, mainly to or through
Singapore.
Properties
The
flesh is exceptionally firm and crisp for a tropical fruit. It is quite
sweet when fully ripe, but unripe fruit is sour and astringent due to
the presence of a little tannic acid. When the fruit is ripe, a layer
of granular-looking flesh
Description
A relatively small, usually dioecious, very spiny, creeping and
tillering palm, growing in compact clumps formed by successive
branching at the base. Roots not extending to great depth. Stem a
mostly subterranean stolon with only its terminal leafbearing part more
upright, reaching a length of several metres and 10-15 cm in diameter,
often branching; new roots growing out of the stem immediately under
the crown of leaves; internodes very congested, leaf traces inserted
almost horizontally.
Leaves pinnate, 3-7 m long;
leaf-sheaths, petioles and leaflets armed with numerous, long, thin,
grey to blackish spines; leaflets 20-70 cm × 2-7.5 cm.
Inflorescence an axillary compound spadix, stalked, at first enclosed
by spathes; male inflorescence 50-100 cm long, consisting of 4-12
spadices, each 7-15 cm × 0.7-2 cm, female one 20-30 cm long, composed
of 1-3 spadices, 7-10 cm long.
Flowers in pairs
in axils of scales; staminate flowers with reddish, tubular corolla and
6 stamens borne on the corolla throat and a minute pistillode;
pistillate ones with tubular corolla, yellow-green outside and dark red
inside, a trilocular ovary with short trifid, red style and 6
staminodes borne on the corolla throat.
Fruit a
globose to ellipsoid drupe, 15-40 per spadix, ca. 5-7 cm × 5 cm,
tapering towards base and rounded at top; epicarp (skin) comprised of
numerous yellow to brown, united, imbricate scales, each scale ending
in a fragile prickle.
Seeds usually 3 per fruit,
with 2-8 mm thick, fleshy, cream-coloured sarcotesta and a smooth,
stony inner part, 23-29 mm × 15-27 mm, which is blackish-brown and
trigonous with 2 flat surfaces and a curved one; endosperm homogeneous
and white.
Growth and development
Seed kernels taken directly
from the fresh fruit germinate readily in less than a week under moist,
shady conditions, even on top of the soil. After removal from the fruit
the kernels quickly lose viability in storage, probably because the
embryo dries out irreversibly: 55% germination was found after 1 week,
0% after 2 weeks. Germination becomes visible when the cylindrical
embryo-containing plug is extruded through the germpore at the kernel's
apex. A radicle soon emerges from the tip of the plug and the shoot, a
main root and several secondary roots emerge from the sides of this
plug. About 60-90 days after sowing the first complete leaf, bifid and
some 20-30 cm long, is fully expanded, the seedling still being firmly
attached to the kernel. The palm starts flowering three to four years
after sowing.
Pollination is probably by insects, notably a weevil,
tentatively identified as Nodocnemis sp. In Queensland, Australia,
pollen is carried from palm to palm by curculionid beetles, large
numbers of which visit the flowers. The fruits are mature five to seven
months after pollination. In principle, the palm flowers and fruits
continuously, but most reports indicate harvest peaks around May and -
a major one - around December in Indonesia. This implies a top fruit
set in June-July, i.e. the first half of the dry season, following the
small harvest peak. The palm can be productive for 50 years or more.
Other botanical information
The
salak palm grown in northern Sumatra is ascribed to a distinct species,
S. sumatrana Becc. The species S. zalacca, which is cultivated
elsewhere in Indonesia, is subdivided into two botanic varieties, var.
zalacca from Java and var. amboinensis (Becc.) Mogea from Bali and
Ambon. In Indonesia at least 20 intraspecific taxa are distinguished
according to place of origin and cultivation, e.g. "Condet", "Pondoh",
"Bali", "Suwaru"; these may obtain cultivar status as vegetative
propagation gains importance. "Bali" is monoecious; the inflorescences
bear both hermaphrodite and staminate flowers; the latter produce
functional pollen.
Ecology
Salak thrives under humid tropical
lowland conditions. In the main production centres, average annual
rainfall is between 1700 and 3100 mm. Because of its superficial root
system, the palm requires a high water table, rain or irrigation during
most of the year, but it does not stand flooding. Fruit yield and
quality in Java diminish above 500 m altitude. Salak is usually grown
under shade. Soil types in production centres include podzolic soils
and regosol
Propagation and planting
Seeds are sown directly
in the field (2-5 seeds together in 5 cm deep holes) or in nursery
beds. The seedlings are planted out in the field during the rainy
season when they are a few months old. Vegetative propagation is less
common. It involves removing rooted lateral offshoots from older
plants, or, with higher rates of success, layering or air layering
3-6-month-old shoots. Young palms require heavy shade which may be
reduced after about one year. Salak palm, especially when young, is
intercropped in mixed gardens with banana, mango and Artocarpus spp.
Male trees are maintained at a rate of 2-20%, evenly dispersed among
the female trees or as guard rows around them. Plant distances
encountered vary from less than 2 m to 6 m.
Husbandry
Weeding
is necessary before the leaf canopy is closed. Basal suckers are
usually cut out in order not to lower the fruit yield of the mother
palm. Lateral shoots may be spared to grow into fruiting stems or to be
used for vegetative propagation. If the erect portion of the stem grows
too tall, the palm loses vitality, probably because the young roots
formed immediately under the crown cannot reach the soil. To rejuvenate
the palm, farmers usually push the stem back into the ground and earth
it up. Ageing plant parts are cut off and either buried between the
palms or burned, the ash being used as fertilizer. Adequate use of
fertilizers may make shading in salak cultivation less necessary than
is generally assumed. Farmyard manure as well as urea, triple
superphosphate and potassium muriate are reported to have been tried by
farmers. Fruit taste may be negatively or positively influenced by
fertilizing. Exclusive use of urea is said to produce large but
perishable fruits, and also to cause strong vegetative growth which
increases the risk of the palms toppling over. Irrigation is necessary
during the dry season if the superficial root system of the palm cannot
reach the water table.
In many places hand pollination is practised
by tapping a flowering male spike held above a female inflorescence.
Fruit bunches are usually thinned to provide space for the remaining
fruits to grow larger. The supporting leaf of a bunch is sometimes
pruned to ensure undisturbed development of the bunch. In some places
the bunch is tied up because it is believed that if it develops hanging
down, the taste is less good.
Diseases and pests
In Java a
fungus disease provisionally identified as Mycena sp. sometimes occurs,
especially during the wet season; white mycelium overgrows the bunch
and fruits finally rot. The fungus Pestalotia sp. causes black spots on
the leaves; growers attempt to check the disease by cutting and burning
affected leaves. Pink disease (Corticium salmonicolor) can cause
serious loss of fruit and plants. Control depends largely on reducing
the infection pressure by early removal of diseased parts; proper
ventilation to lower the humidity in the crop is also important.
Larvae
of the weevils Omotemnus miniatocrinitus and O. serrirostris which
tunnel into the top of the palm, and of the weevil Nodocnemis sp. which
bore into the young fruit bunches, are occasionally harmful. On the
other hand, the latter insect is a pollinator. Growers control weevils
by poking a piece of wire into the holes. There are reports of an
unidentified grub feeding on the roots and devastating entire stands of
salak orchards in central Java. Pests reported to feed on salak palm
without indication of harmfulness include the monophagous beetle
Calispa elegans , the polyphagous caterpillar Ploneta diducta , a leaf
roller (Hidari sp.), the scale insect Ischnaspis longirostris and a bug
(Tolumnia sp.), as well as several rodents such as rat and luwak
(Paradoxurus hermaphroditus).
Harvesting
Harvesting takes
place at a fruit age of 5-7 months, or somewhat earlier if rains cause
fruits approaching maturity to swell too quickly and burst. Fruits are
harvested by cutting the bunches with a reaping hook. The seasonality
generally observed in fruiting (for example, in Java) is probably
caused by the negative influence of excessive drought or excessive rain
on flowering and/or pollination. Where palms have access to water
throughout the year (through a high water table or irrigation),
fruiting is indeed more evenly spread over the year.
Yield
The scarce data available suggest that annual yields vary from 5-15 t/ha.
Handling after harvest
Fruits
picked when not too ripe will stand 2 or 3 days of transportation, for
example in bamboo baskets. In a hot and humid climate, fresh fruit will
not last much longer than a week after picking. The slightest injury
accelerates spoiling. There is a need to establish maturity indices for
harvesting and techniques to control fruit rot in order to extend shelf
life. Farmers or retailers often sort salaks into size classes before
selling them.
Genetic resources
Cultivars varying in fruit
size and colour have been selected from the wild forms. Seedless and
monoecious forms occur, especially in Bali. The Salacca Breeding
Laboratory, a private institute in Bogor, has collected virtually all
salak cultivars and species in the genus. They include rare species and
potentially ornamental ones, namely S. dransfieldiana J.P. Mogea, S.
magnifica J.P. Mogea, S. minuta J.P. Mogea, S. multiflora J.P. Mogea
and S. ramosiana J.P. Mogea.
Breeding
Both intraspecific and
interspecific breeding has been taken up by the Bogor laboratory. In
Chanthaburi, Thailand, the Department of Agriculture started a breeding
programme in 1985 to improve S. wallichiana Mart., including crosses
with S. zalacca.
Prospects
Salak
cultivation is very likely to expand in Java, especially around the big
cities where salak is constantly in demand and fetches high prices.
Once the first unproductive years are overcome, a salak garden may be
quite profitable because relatively few inputs are needed to keep it in
production. Prospects for exports are limited because of the
perishability of the fresh fruits, and trade in general would benefit
greatly if shelf life could be extended. There seems to be great scope
for an increase in productivity. Improvement of vegetative propagation
techniques would facilitate the dispersal of selected high quality
cultivars.
Literature
de Jong, W.H., 1934/35. Salakcultuur en
-handel in de regentschappen Malang en Pasoeroean. [Salak culture and
trade in the Malang and Pasuruan regencies]. Landbouw (Buitenzorg)
10(11): 439-450.
Miller, R.H., 1977. Fruit, germination and
developmental morphology of Salacca edulis palm seedling.
Phytomorphology (India) 27(3): 282-296.
Mogea, J.P., 1982. Salacca zalacca, the correct name for the salak palm. Principes 26(2): 70-72.
Moncur,
M.W., 1988. Floral development of tropical and subtropical fruit and
nut species. CSIRO, National Resources Series No 8, Melbourne. pp.
127-130.
Tjahjadi, N., 1989. Bertanam salak [Salak growing]. Kanisius, Yogyakarta, Indonesia. 39 pp.
Yoe
Edy, 1986. Melacak jenis-jenis salak yang paling enak + Bertanam salak
[Overview of the best salak types + Salak growing]. Trubus (Indonesia)
17 (197): 7-12.
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