The rambutan flourishes from sea-level to 1,600 or even 1,800 ft (500-600 m), in tropical, humid regions having well-distributed rainfall. In the ideal environment of Oriental Mindoro Philippines, the average temperature year-round is about 81º F (27.3º C), relative humidity is 82%, rainfall 71 in (180 cm)-about 165 rainy days. The dry season should not last much over 3 months.
The tree does best on deep, clay-loam or rich sandy loam rich in organic matter, or in deep peat. It needs good drainage.
Rambutan seeds, after removal from the fruit and thorough washing, should be planted horizontally with the flattened side downward in order that the seedling will grow straight and have a normal, strong root system. Seeds will germinate in 9 to 25 days, the earlier, the more vigor in the seedling. The rate of germination of 2-day-old seeds is 87% to 95%. A week after seed removal from the fruit, there may be only 50% to 65% germination. Sun-drying for 8 hours and oven-drying at 86º F (30º C) kills seeds within a week. Washed seeds will remain viable in moist sawdust, sphagnum moss or charcoal for 3-4 weeks, and some will even sprout in storage. The juice of the flesh inhibits germination. Accordingly, unwashed seeds or seeds treated with the juice can be held for a month in moist sawdust without sprouting.
Rambutan seedlings bear in 5-6 years, but the ratio of female to male trees is 4 or 5 to 7. One Philippine seedling orchard was found to have 67% male trees. Then, too, hardly 5% of female trees give a profitable yield. Vegetative propagation is essential.
Cuttings have been rooted experimentally under mist and with the use of growth-promoting hormones, but this technique is not being practiced. Air-layering may at first appear successful, but many air-layers die after being transplanted into 5-gal containers, or, later, in the field, long after separation from the mother tree.
Marching is very effective onto 5- to 9-month-old seedlings of rambutan or of pulasan (N. mutabile L.) or N. intermedium Radlk., but is a rather cumbersome procedure. After 2 or 3 months, the scion is notched 3 times over a period of 2 weeks and then severed from the parent tree. Cleft-, splice-, and side-grafting are not too satisfactory. Patch-budding is preferred as having a much greater rate of success. Seedlings for use as rootstocks are taken from the seedbed after 45 days and transplanted into 1-quart cans with a mixture of 50% cured manure and later transferred to 5 gal containers. In Oriental Mindoro Province, if the budding is done in the month of May, they can achieve 83.6% success; if done in June and July, 82%. Budded trees flower 2 1/2 to 3 years after planting in the field.
In the Philippines, it is recommended that the trees be planted at least 33 ft (10 m) apart each way, though 40 ft (12 m) is not too much in rich soil. If the trees are set too close to each other, they will become overcrowded in a few years and production will be seriously affected.
Philippine agronomists apply 2.2 lbs (1 kg) ammonium sulfate together with 2.2 lbs (1 kg) complete fertilizer (12-24-12) per tree immediately after harvest and give the same amount of ammonium sulfate to each tree near the end of the rainy season. Studies in Malaya show that a harvest of 6,000 lbs/acre (6,720 kg/ha) of rambutan fruits removes from the soil 15 lbs/acre (approximately 15 kg/ha) nitrogen, 2 lbs/acre (2 kg/ha) phosphorus, 11.5 lbs/acre (11.5 kg/ha) potassium, 5.9 lbs/acre (5.9 kg/ha) calcium, and 2.67 lbs/acre (2.67 kg/ha) magnesium.
Irrigation is given as needed in dry seasons. Light pruning is done only to improve the form of the tree and strengthen it. Rambutan trees should be sheltered from strong winds which do much damage during the flowering and fruiting periods.
In Malaya, the rambutan generally fruits twice a year, the first, main crop in June and a lesser one in December. In the Philippines, flowering occurs from late March to early May and the fruits mature from July to October or occasionally to November.
The entire fruit cluster is cut from the branch by harvesters. If single fruits are picked, they should be snapped off with a piece of the stem attached, so as not to rupture the rind. The fruits must be handled carefully to avoid bruising and crushing, and kept dry, cool, and well-ventilated to delay spoilage.
Generally, shoots that bear fruit one year will put out new growth and will bloom and fruit the next year, so that biennial bearing is rare in the rambutan. However, yield may vary from year to year. Individual trees 8 years old or older have borne as much as 440 lbs (200 kg) one season and only 132 lbs (60 kg) the next. In the Philippines, the average production per tree of 21 selections was 264 lbs (120 kg) over a 4-year period, while the general average is only 106 lbs (48 kg).
From 1965 to 1967, agronomists at the College of Agriculture, University of the Philippines, studied the growth, flowering habits and yield of the Indonesian cultivars, ‘Seematjan’, ‘Seenjonja’, and ‘Maharlika’. They found that all the ‘Seematjan’ flowers were hermaphrodite functioning as female (h.f.f.) and that it is necessary to plant male trees with this cultivar. ‘Seenjonja’ and ‘Maharlika’ flowers were mostly h.f.f. with a very few hermaphrodite functioning as males (h.f.m.) in the same panicles, and concluded that, though self-pollination is possible, planting of male trees with these cultivars should improve production.
Ordinarily, the fruits must be gotten to local markets within 3 days of picking before shriveling and decay begin. Fungicidal applications and packing in perforated polyethylene bags have extended fresh life somewhat. Weight loss has been reduced by packing in sawdust, or coating with a wax emulsion. Storing in sealed polyethylene bags at 40º F (10º C) and 95% relative humidity has preserved the fruits in fresh condition for 12 days. Some cultivars, as noted, keep better than others.
Pests and Diseases
Few pests or diseases have been reported by rambutan growers. Leaf-eating insects, the mealybug, Pseudococcus lilacinus, and the giant bug, Tessaratoma longicorne, may require control measures. The mango twig-borer, Niphonoclea albata, occasionally appears on rambutan trees. The Oriental fruit fly attacks very ripe fruits. Birds and flying foxes (fruit-eating bats) consume many of the fruits, probably considerably reducing yield figures.
There are several pathogens that attack the fruits and cause rotting under warm, moist conditions. Powdery mildew, caused by Oidium sp., may affect the foliage or other parts of the tree. A serious disease, stem canker, caused by Fomes lignosus in the Philippines and Ophioceras sp. in Malaya, can be fatal to rambutan trees if not controlled at the outset.
Rambutans are most commonly eaten out-of-hand after merely tearing the rind open, or cutting it around the middle and pulling it off. It does not cling to the flesh. The peeled fruits are occasionally stewed as dessert. They are canned in sirup on a limited scale. In Malaya a preserve is made by first boiling the peeled fruit to separate the flesh from the seeds. After cooling, the testa is discarded and the seeds are boiled alone until soft. They are combined with the flesh and plenty of sugar for about 20 minutes, and 3 cloves may be added before sealing in jars. The seeds are sometimes roasted and eaten in the Philippines, although they are reputedly poisonous when raw.
Rambutan are rich in vitamin C, they are also a good source of Potassium, Sodium, Phosphorus, Magnesium and traces of many other minerals. Rambutan are a great tasting, healthy addition to anyones diet, though diabetics should be aware of their high sugar content.
The pericarp (rind) of Rambutan contains saponin and tannin and in Java it is dried and used medicinally. The seeds contain tallow which has a high level of arachidic acid and is sometimes used to make soap and candles. The seed of the Rambutan should not be eaten raw due to its high level of toxicity and is also said to be narcotic.
There are traces of an alkaloid in the seed, and the testa contains saponin and tannin. The seeds are said to be bitter and narcotic. The fruit rind also is said to contain a toxic saponin and tannin.
Seed fat: the seed kernel yields 37-43% of a solid, white fat or tallow resembling cacao butter. When heated, it becomes a yellow oil having an agreeable scent. Its fatty acids are: palmitic, 2.0%; stearic, 13.8%; arachidic, 34.7%; oleic, 45.3%; and ericosenoic, 4.2%. Fully saturated glycerides amount to 1.4%. The oil could be used in making soap and candles if it were available in greater quantity.
Wood: The tree is seldom felled. However, the wood – red, reddish-white, or brownish – is suitable for construction though apt to split unless carefully dried.
Medicinal Uses: The fruit (perhaps unripe) is astringent, stomachic; acts as a vermifuge, febrifuge, and is taken to relieve diarrhea and dysentery. The leaves are poulticed on the temples to alleviate headache. In Malaya the dried fruit rind is sold in drugstores and employed in local medicine. The astringent bark decoction is a remedy for thrush. A decoction of the roots is taken as a febrifuge.
For additional information, contact:
D.A. Compound, Elliptical Rd.,
Tel. Nos. (632) 929-6065 to 67 / 920-3991 / 928-1134
sources: wisegeek.com, hort.purdue.edu, easymangosteen.com