Common Name: Rakum Palm

General Information

Salacca wallichiana is an evergreen palm with very spiny leaves that are 3 - 7 metres long[]. A creeping and tillering palm that grows in clumps, the creeping, subterranean, unbranched stems can reach 3 - 5 metres long and 20cm in diameter in plants over 100 years old, with an erect terminal leaf-bearing part around 1 metre tall and with many adventitious roots, most abundant towards the tip[]. Roots can reach a length of 2 metres but do not extend to a great depth[].
The plants are valued for their edible fruit, mainly in Thailand, and are also harvested as a source of construction materials. Superior fruit-bearing forms have been developed and these are often cultivated in gardens and plantations[].

Known Hazards

None known

Botanical References

Range

Southeast Asia - Myanmar, Thailand, Malaysia, Indonesia.

Habitat

Lowland rain forest or dry forest, often in wet areas, or commonly planted; at elevations up to 200 metres[].

Properties

Edibility Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	4.00 m
Growth Rate	Slow
Pollinators	Insects
Self-fertile	No
Cultivation Status	Cultivated, Wild

Cultivation Details

Salacca wallichiana is a plant of the hot, moist tropical lowlands[]. It grows in areas where the mean annual rainfall is within the range 2,500 - 3,000mm with a dry season of 5 - 6 months[]. A dry season is needed for good fruit set; spadices emerging in the rainy season tend to rot and the viability of the pollen is poor[]. The temperature range required is 22 - 32°c; lower temperatures reduce flowering[].
Thrives in soils ranging from sandy loam to heavy clay[]. On low-lying wetlands it grows better than most fruit trees[]. Prefers a pH in the range 5 - 6, tolerating 4.5 - 6.5[]. Established plants can stand drought very well but, for a good yield of fruit, irrigation is required in the dry season[]. In its natural habitat and in mixed orchards rakum is commonly found growing under shade, but in commercial orchards the palms can be grown successfully without shade, provided they are irrigated[].
Plants commence flowering when about 5 - 6 years old[]. The plant flowers all year round, the fruit ripening 7 - 9 months after flowering[]. Nearly all fruit set, however, takes place early in the dry season, leading to a very seasonal harvesting of the fruit[].
The average annual fruit yield varies between 6 - 12 t/ha depending on the cultivars.
The skin of 10 - 16 week-old fruitlets is brown, turning darker to almost black at 17 - 23 weeks, gradually changing to orange when the fruit ripens[].
The flesh of 10 - 19 week-old fruits is off-white and turns to light yellow when the fruits are 20 - 22 weeks old; as the fruit grows it gradually assumes a more yellow-orange colour[].
The stones in 10 - 19 week-old fruits are white and contain a jelly-like substance. The colour changes to yellow at 20 - 23 weeks of age and to brown thereafter while the contents harden[].
For the superior sala cultivars, harvesting time is 36 weeks and not later than 38 weeks after pollination[].
At harvest each fruit cluster or the entire infructescence is cut with a hooked knife or pruning shears on long handles[].
In young non-bearing orchards, removing suckers is the most unpleasant chore, but a must. One or two stems per clump are sufficient for good yield[]. Dense clumps yield poorly and are difficult to harvest[].
Leaf pruning is not advisable, but may be necessary to facilitate orchard operations[].
Hand pollination can raise yields substantially[].
Several cultivars with superior fruits have been developed[].
A dioecious species, both male and female forms need to be grown if fruit and seeds are required[]. About 1 male plant to every 15 females is considered sufficient for good pollination[]. Xenia effects are quite noticeable in S. Wallichiana, so it is important to choose a compatible male strain[].

Edible Uses

The acid seeds are utilized as an ingredient in curries[].
The rakum palm is grown for the edible sarcotesta (fleshy seedcoat) of the fruit[]. The sour unripe fruit can be a substitute for lime in cooking, whereas the ripe fruit is sweet and consumed raw[].
For the sweetest fruit, the wild form should be harvested 28 weeks after anthesis (hand pollination). At this age the sugar content is 13 - 14° Brix[]. Fruits over 30 weeks old develop an unpleasant flavour[]. Fruits which are used for cooking can be harvested after 25 weeks[].
The fruit is a drupe, occurring in dense heads, obovoid, 2.5 cm long, the skin (epicarp) consisting of orange-brown scales with reflexed brittle points; endocarp not differentiated[].

Medicinal

None known

Agroforestry Uses:

The wild, spiny form is grown as a fruit-bearing fence[].

Other Uses

Wild clumps in the forest not only produce food, but are also a major source of cork, thatch and other construction materials in rural areas[].

Propagation

Seed - best sown as soon as it is ripe, it quickly loses its viability[]. The fresh seed germinates readily and propagation from seed is easy. Germination usually takes place in less than 10 days, with about 90% germination rate[].
Vegetative propagation of improved forms is usually recommended. Stem sections 1 - 2 metres long are taken from ageing, high-quality clones[]. These are buried in the soil and covered with a mulching material such as rice straw. The soil is kept moist to force viable buds on the cuttings to sprout[]. The plantlets are separated from the stem and nursed in polythene bags for a year before planting out in the field at the beginning of the rainy season[].
Vegetative propagation by separating rooted suckers from the mother palms is less common[].

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