Nephelium (PROSEA Fruits)

Plant Resources of South-East Asia Introduction

List of species

Nephelium L.

Protologue: Mant. Pl.: 18 (1767).

Family: Sapindaceae

Chromosome number: x= 11; 2n not known for most species.

Major species and synonyms

• Nephelium cuspidatum Blume, Rumphia 3: 110 (1847), synonyms: Nephelium eriopetalum Miq. (1861), Nephelium ophiodes Radlk. (1879), Nephelium robustum Radlk.(1913).

• Nephelium hypoleucum Kurz, J. Asiat. Soc. Bengal 40, Pt. 2 Nat. Hist.: 50 (1871), synonyms: Nephelium cochinchinense Pierre (1895), Nephelium longana Cambess. var hypoleuca King (1896).

• Nephelium lappaceum L. - see separate article.

• Nephelium maingayi Hiern, Fl. Brit. India 1: 688 (1875), synonyms: Nephelium glabrum auct. non Noronha: King (1896), Ridley (1922), Corner (1978).

• Nephelium rambutan-ake [sic, correct name: Nephelium ramboutan-ake] (Labill.) Leenh. Blumea 31: 415 (1986) , synonyms: Nephelium mutabile Blume (1847), Nephelium intermedium Radlk. (1904), Nephelium philippense Monsalud et al. (1966).

• Nephelium uncinatum Radlk. ex Leenh., Blumea 31 (2): 421 (1986).

Vernacular names

General:

• rambutan.

N. cuspidatum var. eriopetalum :

• Indonesia: deket, rambutan kabung, ranggung
• Malaysia: sanggul lotong.
• Singapore: sanggul lotong.

N. cuspidatum var. robustum :

• Malaysia: giant rambutan (Sabah).

N. hypoleucum :

• Burma: kyet-mouk, tawthayet
• Cambodia: semon, sao mao
• Laos: co lenh
• Thailand: kho laen, mak waeo
• Vietnam: cây thu'an.

N. maingayi :

• Indonesia: ridan, penjaih, buah unjing (Sumatra)
• Malaysia: kedin, buah raydun, ronjo (Peninsular Malaysia).

N. ramboutan-ake :

• Indonesia: kapulasan
• Malaysia: pulasan (Peninsular), meritam (Sabah, Sarawak)
• Philippines: bulala (Tagalog)
• Thailand: ngoh-khonsan.

N. uncinatum :

• Indonesia: namun, lomon (Kalimantan)
• Malaysia: mentaokod.

Origin and geographic distribution

The genus Nephelium is centred in Peninsular Malaysia, with a few penetrations into continental Asia, the Philippines and Borneo. In total 22 species are recognized; 5 occur in Burma, Thailand and Indo-China, 13 in Peninsular Malaysia (3 endemic), 16 in Borneo (8 endemic), 4 in the Philippines, 3 in western Java and 1 in Sulawesi. N. cuspidatum occurs in Burma, Thailand, Indo-China and the whole Malesian region, except in Papua New Guinea. N. hypoleucum occurs in Burma, Thailand and Indo-China. N. maingayi and N. uncinatum occur in Peninsular Malaysia, Sumatra and Borneo. N. ramboutan-ake occurs in India (Assam), Burma, Indonesia, Malaysia and the Philippines; it is often cultivated as well.

Except for some introductions in northern Australia, the minor species are not cultivated outside the regions mentioned above.

Uses

The fruits of most minor Nephelium species are more or less sweet and appreciated by the local people, when available. They resemble the cultivated rambutan in shape and colour, but the edible sarcotesta is thinner and less sweet, or even sour, and often adheres tightly to the seed kernel. The timber of some species is locally used as firewood.

Production and international trade

The minor Nephelium species are only rarely and locally traded. The fruiting season is very short, resulting in low prices, e.g. 200-250 Rp/kg in Indonesia in the 1980s.

Properties

The fruit of N. ramboutan-ake contains per 100 g edible portion: water 85 g, protein 0.8 g, fat 0.6 g, carbohydrates 13 g, fibre 0.1 g and ash 0.4 g. Neither the properties of the fruit nor those of the timber of the other minor Nephelium species have been described. Fruits of wild trees of N. cuspidatum var. robustum are often very sour, whereas fruits from village orchards can be very sweet and juicy. It is assumed that, owing to their large size, wild trees are often felled to get at the fruit, resulting in a genetic leach towards sour types in the forests.

Description

• Medium to large, dioecious or monoecious trees, rarely shrubs, sometimes with buttresses.
• Leaves spirally arranged, paripinnate, 1-5(-18)-jugate; leaflets alternate or rarely opposite, coriaceous to chartaceous.
• Inflorescences usually terminal, sometimes axillary; flowers regular, calyx (4-)5(-6)-merous, corolla with 5(-6) well developed petals or lacking or 1-4 petals reduced; disk complete, often lobed; stamens 4-10; pistil densely hairy, ovary warty, (1-)2(-4)-loculed.
• Fruit an ellipsoid to subglobular schizocarp, warty to spiny, exceptionally nearly smooth, splitting into 1-3 mericarps (nutlets).
• Seed with sarcotesta usually covering the whole seed.
• Seedling with epigeal germination, the first true leaf already paripinnate.

N. cuspidatum.

• Tree or shrub, up to 40 m tall, trunk 80 cm in diameter, sometimes with buttresses.
• Leaves (1-)2-9(-13)-jugate, petiole 2.5-21 cm long, petiolules 2-7.5(-15) mm; leaflets 6-35 cm × 1.75-12.5 cm, 1.5-5 times as long as wide, drooping.
• Inflorescences (pseudo)terminal, also ramiflorous or cauliflorous, long pendulous racemes or spikes; petals often absent; stamens (4-)7 or 8(-9); pistil 2-merous.
• Fruit ellipsoid to globular, 2-4 cm × 2-3 cm, glabrous, densely set with up to 2 cm long appendages, red.

N. hypoleucum.

• Tree up to 30 m tall, trunk 1.40 m in diameter, with buttresses up to 1.5 m tall.
• Leaves 1-4(-5)-jugate, petiole 3-16 cm long, petiolules (3-)5-11 mm; leaflets 6.5-30 cm × 2-8 cm, (1.5-)2-3(-4.5) times as long as wide.
• Inflorescences terminal and axillary, male and female flowers sometimes in same inflorescence; petals 0-6; stamens 7-10; pistil 2-3-merous.
• Fruit ellipsoid, 2-3 cm × 1.5-2.25 cm, rather densely warty, warts up to 1.5 mm high, red.

N. maingayi.

• Tree up to 40 m tall and 90 cm diameter, trunk sometimes with buttresses up to 1.40 m tall.
• Leaves 1-foliolate to 3-5-jugate; petiole 1-10 cm long, petiolules 4-17.5 mm; leaflets 6-22 cm × 3-9 cm, 1.5-3.5 times as long as wide.
• Inflorescences axillary to terminal; petals absent; stamens 4-6; pistil 1-merous.
• Fruit flattened ellipsoid, 2-2.75 cm × 1.25-1.75 cm × 1-1.25 cm with a 2-3 mm long stipe and hook-like remnant style above the stipe, variably warty, red, brown or black.

N. ramboutan-ake.

• Tree, up to 15(-36) m tall.
• Leaves 1-7-jugate, petiole up to 11 cm long, petiolules up to 12.5 mm; leaflets 4-20 cm × 2-11 cm, 2-4 times as long as wide.
• Inflorescences axillary to pseudoterminal; petals absent; stamens 5-8; pistil 2(-3)-merous.
• Fruit ellipsoid to subglobular, 4-6.5 cm × 2.5-5 cm, densely coarsely spiny with spines up to 1.5 cm long, reddish, yellowish, or blackish.
• Seed with white sarcotesta.

N. uncinatum.

• Tree up to 24 m tall, trunk 45 cm in diameter, buttresses up to 1.5 m tall.
• Leaves (1-)3-7(-18)-jugate, petiole 3-9 cm long, petiolules 2-4 mm; leaflets 5-11 cm × 1.5-3.5 cm, 2.5-6 times as long as wide.
• Inflorescences terminal and axillary; petals absent; stamens 5-6, pistil 1-2-merous.
• Fruit ellipsoid to subglobular, 3 cm × 2.25 cm, sparsely set with thick warts tapering into up to 7.5-mm long appendages, red.

Growth and development

Flowering and fruiting of the minor Nephelium species depends largely on the seasonality of the climate and does not necessarily occur annually. Apparently the species need a definite, but not excessive, dry season for good flowering and heavy fruit set. For example, an excellent crop was produced in Borneo in February and March 1987 after a very dry August and a moderately dry September in 1986. In several species, trees bear either male or bisexual flowers. These species are effectively dioecious since little or no viable pollen is produced in the anthers of bisexual flowers. Pollination is by insects, mainly bees.

Other botanical information

N. cuspidatum is a complex species and has been subdivided into 6 varieties, 2 of which split further into 2 subvarieties. Two varieties are known to be mainly grown for the fruit:

• var. eriopetalum (Miq.) Leenh. Leaflets oblong, 3-12.5 cm wide. Peninsular Malaysia, Sumatra, Java, Borneo.

• var. robustum (Radlk.) Leenh. Leaflets linear, 10-35 cm × 5-10 cm. Sarawak, Brunei, Kalimantan, Sabah, the Philippines (Palawan).

N. ramboutan-ake is a variable species and may closely resemble N. lappaceum . The spines on the fruits are usually short and stubby in N. ramboutan-ake and long filiform in N. lappaceum.

The taxonomy of the minor Nephelium species needs more study. In Borneo several edible rambutans, which cannot be attributed to the taxa described so far, are distinguished and named.

Ecology

Most species are typically middle storey trees of the lowland tropical rain forest, but occur also in old secondary forest where they have often been introduced by people who, for instance, planted the seed in swidden fields. They are largely confined to hills, ridges and slopes, on sandy, yellow sandy clay or clay soils. N. hypoleucum occurs mostly in evergreen, sometimes in deciduous, forest; also on savannas in hilly country, mainly on fertile sandy soils, at low to medium altitudes up to 1200 m. N. ramboutan-ake occurs mostly in lowland primary forests, often on river banks but rarely in swamps, usually on sand or clay. N. maingayi is tolerant to peat swamps and periodically flooded river banks.

Agronomy

Where minor Nephelium species are planted, propagation is by seed, although vegetative propagation may be possible, as in rambutan. The cultivation of N. ramboutan-ake is similar to N. lappaceum, but in general the trees require less space. It is said to be less productive than the rambutan. People and animals play a major role in the dissemination of most of the non-cultivated species of Nephelium, particularly in home gardens of indigenous people. It is not known whether intestine passage improves germination. N. cuspidatum var. eriopetalum and var. robustum are frequently cultivated in home gardens of Borneo. N. maingayi and N. uncinatum are sometimes planted, or at least spared when the land is cleared.

The trees are often infected by powdery mildew, which is also found on the fruit but does not seriously affect their quality. No other diseases or pests have been reported. There is no information on yield levels. Harvesting of tall trees is difficult.

Genetic resources and breeding

Nephelium germplasm collections in South-East Asia are only just now being enriched by accessions of the minor species. Selection work should be aimed at "freestone" fruit, with flesh that separates easily from the seed kernel, and at trees that come into bearing early and remain small, for instance by using appropriate rootstocks.

Prospects

Commercial production of N. ramboutan-ake could be expanded. Its ecological requirements are much the same as for the rambutan, while its fruits often are slightly sweeter and larger. The fresh, slightly sour taste of some of the wild species is preferred by many consumers to the very sweet taste of most rambutan cultivars. This opens a favourable long-term perspective for the wild species, in particular for the large-fruited varieties of N. cuspidatum.

Literature

• Leenhouts, P.W., 1986. A taxonomic revision of Nephelium (Sapindaceae). Blumea 31: 373-436.
• Meijer, W., 1969. Fruit trees in Sabah (North Borneo). Malayan Forester 32(3): 252-265.
• Tankard, G., 1987. Exotic tree fruit for the Australian home garden. Recent rare fruit discoveries in Malaysian Borneo. Thomas Nelson Australia, Melbourne, Victoria. pp. 117-125.
• van Welzen, P.C., Lamb, A. & Wong, W.W.W., 1988. Edible Sapindaceae in Sabah. Nature Malaysiana 13(1): 10-25.

Authors

B. Seibert