- Protologue: Sp. Pl. 1: 428 (1743); Gen. Pl. ed. 5: 196 (1754).
- Family: Oxalidaceae
- Chromosome number: 2n= 22, 24
- Averrhoa bilimbi L., Sp. Pl. 1: 428 (1753).
- Averrhoa carambola L., Sp. Pl. 1: 428 (1753).
- Bilimbi, cucumber tree (En)
- Cornichonier (Fr)
- Indonesia, Malaysia: belimbing asam, blimbing wuluh, belimbing buluk
- Philippines: kamias, iba (Tagalog)
- Cambodia: trâlông töng
- Thailand: taling pling
- Vietnam: khê tau.
- Carambola, star fruit (En)
- Carambolier (Fr)
- Indonesia, Malaysia: belimbing manis
- Philippines: balimbing
- Cambodia: spö
- Laos: füang
- Thailand: ma fueang
- Vietnam: khê.
Origin and geographic distribution
Some authors seek the origin in tropical America (Brazil), from where it supposedly was taken to the Philippines. However, most authors support the South-East Asian origin, for instance because there is a Sanskrit name for carambola. Moreover, the distribution of bilimbi in tropical America can be traced to its introduction from Timor to Jamaica in 1793. Both crops are now grown all over the humid tropics, and carambola also in the subtropics.
The fruit of bilimbi is used for pickles, curries, chutney and preserves in syrup. The fruit of carambola is used fresh, in salads, punch bowls, juice, preserves, jam and jelly. Both fruits are also used to clean metal and remove stains and in various ways in traditional medicine (e.g. skin disorders, fevers).
Production and international trade
The only South-East Asian data on areas and production are from the Philippines, where 78 000 carambola trees yielded 2150 t of fruits in 1977, and Malaysia which produced 3443 t of carambola in 1985. Both crops grow mainly in home gardens. Carambola is grown commercially and is flown to European markets, from Israel as well as from Malaysia.
The sour taste of bilimbi is largely determined by citric acid; oxalic acid dominates in carambola, even in the sweet types. Both fruits are rich in potassium and vitamin A; the vitamin C content is low in bilimbi and fair in carambola.
Quantitative data for the composition of carambola per 100 g edible portion: water 90 g, protein 0.75 g, total sugars 3.5-11 g, fibre 0.7 g. Carambola fruit contains 60-75% juice, which may be quite acid or sweet as indicated by the acidity range (1.9-13.1 m.eq./100 g) and Brix levels (5-13%).
- Small trees, 6-9 m tall, carambola up to 15 m.
- Leaves imparipinnate with entire, usually ovate leaflets.
- Flowers in axillary or cauliflorous panicles, pentamerous, heterostylous, with petals much longer than sepals, 10 stamens, of which 5 sometimes rudimentary, and a superior, 5-celled ovary with 5 styles.
- Fruit a large berry, (ob)ovoid to ellipsoid in outline.
- Seeds ellipsoid; endosperm present.
- Sparsely branched tree, branches stiff, thick, upright.
- Leaves 7-19-jugate.
- Flowers usually in cauliflorous panicles, heterotristylous; petals free, 10-20 mm long, red-purple; short stamens fertile.
- Fruit slightly lobed, up to 10 cm × 5 cm.
- Seeds lacking aril.
- Much-branched, broad, bushy tree, branches usually drooping.
- Leaves 3-6-jugate.
- Flowers usually in axillary panicles, heterodistylous; petals coherent, up to 8 mm long, light red with purple heart; short stamens rudimentary, lacking anthers.
- Fruit with 5 pronounced ribs, stellate in cross-section, up to 12.5 cm × 6 cm.
- Seeds with fleshy aril.
Growth and development
Clonal trees bear in 2-3 years, seedlings after 5-6 years. Both species grow, flower and fruit continuously, but usually there are one or two pronounced harvest seasons, each lasting about 2 months. Trees flower abundantly, and overbearing is common in carambola (for a good crop only about 0.5% of the flowers need to be pollinated). Flowers open from 8-10 a.m.; fruit set is usually good but later fruit fall tends to limit the crop. Carambola flowers with long styles are self-fertile, but trees with short-styled flowers as a rule require pollen from long-styled flowers. Fruit ripens 90-110 days after anthesis.
Other botanical information
Carambola cultivars are "Maha 66" and "B1"..."B17", in particular "B2", "B10" and "B11" (Malaysia), "Fu'ang Tung" (Thailand), "Dah Pon" and "Tean Ma" (Taiwan), "Arkin", "Kara" and "Kary" (Florida), "Icambola" (Colombia), "Fwang Tung", "Giant Siam", "Kembangan", "B1", "B2", "B4", "B6", "B10" and "B16" (Australia). Important cv. characters are: taste (sweet to acid, but may be strongly influenced by oxalic acid and tannin content), colour (green to yellow), and shape (thin and sharp-edged wings to thick wings and rounded edges, important in transport).
Both species prefer a climate with a dry season, thriving where teak ( Tectona grandis L.f.) is at home, but also do well in wetter climates. Carambola can be extended to frost-free subtropics; it is grown to 30°S in Australia and 32°N in Israel. Bilimbi grows up to 500 m altitude on Java. Both species have a high water requirement, but they need well-drained soils, pH 5.5-6.5, and grow well on peat. Drought, flooding and salinity are not tolerated. Wind breaks are recommended on exposed sites.
Propagation and planting
Bilimbi is grown mainly from seed. Grafting and budding are successful in carambola. Budwood should not be tender or brittle. Budding on one-year-old rootstocks gives best results. Topworking of trees with cultivars which gain favour is easy; such trees resume production within 1-1.5 years. The standard spacing 6 m × 6 m, that is 277 trees/ha for both species. However, for carambola spacing should be adjusted to growing conditions, ranging from 160 trees/ha in favourable tropical areas to 500 trees/ha in the subtropics and at higher elevations.
Cultivars must be planted mixed for cross-pollination. Pruning, water availability and nutrient supply affect the flowering flushes. In Taiwan carambola trees are pruned to restrict tree size, but hard pruning suppresses flowering. Mulching and irrigation limit water stress. An NPKMg formula, e.g. 10-10-10-5, at about 100 g/tree, is applied every 3 months on young trees; later on the quantity is adapted to trunk girth. Deficiencies of Zn, Mn and Fe must be corrected regularly. In Malaysia, carambola fruit is bagged and excess fruit thinned for top quality.
Diseases and pests
Leaf spot (Cercospora averrhoa) and pink disease (Corticium) occur in South-East Asia, but post-harvest rots are more serious, at least on carambola fruit; the slightest blemish invites infection by Ceratocystis, Colletotrichum, Dothoriella and Phomopsis fungi. Caterpillars (Pingasa, Pseudoterpna, Diacotrichia) attack flowers and young leaves. Carambola fruit suffers most from fruit fly maggots, particularly Dacus dorsalis (South-East Asia) and fruit piercing moth (Othreis spp., Australia); bagging prevents infestation.
Carambola fruit is non-climacteric and is picked green or more mature, depending on the cultivar and consumer preference for a specific taste. The fruit should be gently picked by hand to limit post-harvest losses. Seasonal harvest greatly facilitates commercialization, but for home consumption year-round cropping is an asset.
From 50-300 kg/tree is reported for carambola. At 277 trees/ha, this means 14-80 t/ha per year, confirming that carambola is one of the very few tropical fruits which is naturally prolific.
Handling after harvest
Carambola can be stored 4 weeks at 5-10°C in a room with high humidity, if picked as soon as the fruit starts to turn yellow.
Whereas no developments are foreseen in the case of bilimbi, carambola is rapidly developing into a more commercial crop and penetrating distant markets. Spurred by increasing attention to fruit quality (specific cultivars for different uses, fruit thinning and bagging, harvest on the basis of maturity indices, careful handling of the fruit), the end of the expansion is not yet in sight.
- Coronel, R.E., 1986. Promising fruits of the Philippines. 2nd ed. College of Agriculture, University of the Philippines, Los Baños. pp. 51-60.
- Morton, J.F., 1987. Fruits of warm climates. Creative Resource Systems, Inc. Winterville, N.C., USA. pp. 125-129.
- Popenoe, W., 1920. Manual of tropical and subtropical fruits. MacMillan, New York. pp. 429-432.
- Sedgley, M., 1984. Oxalidaceae. In: Page, P.E. (Editor): Tropical tree fruits for Australia. Queensland Department of Primary Industries, Brisbane. pp. 125-128.
- Watson, B.J., George, A.P., Nissen, R.J. & Brown, B.I., 1985. Carambola: a star on the horizon. Queensland Agricultural Journal 114: 45-51.
Sources of illustrations
Averrhoa carambola: Ochse, J.J. & Bakhuizen van den Brink, R.C., 1931. Vruchten en vruchtenteelt in Nederlandsch Oost Indië. G. Kolff & Co., Batavia. p. 90, Pl. 37. Redrawn and adapted by P. Verheij Hayes.
- J.A. Samson