Common Name: Carambola

General Information

Averrhoa carambola is a small but fast growing, much-branched, evergreen tree usually growing 3 - 5 metres tall but sometimes reaching a height of 10 metres. The short bole can be 15cm in diameter[, ].
A multipurpose tree providing a very popular fruit as well as having a range of medicinal and other uses. It is often cultivated for its fruit, but mainly in gardens, and is generally only sold in local markets because the fruit is extremely perishable and therefore difficult to get to more distant markets[]. The plant is also often grown as an ornamental[].

Known Hazards

None known

Botanical References

Range

E. Asia - Malaysia.

Habitat

Humid forests and woodland on sandy loam[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	4.00 m
Growth Rate	Medium
Pollinators	Bees, Flies
Self-fertile	No
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Plants grow best in the hot humid tropics up to an elevation of around 1,200 metres, though they will tolerate some cool weather and can be grown in subtropical areas[, , ]. It grows best in areas where annual daytime temperatures are within the range 24 - 30°c, but can tolerate 5 - 39°c[]. Mature plants can be killed by temperatures of -2°c or lower, although young growth is badly damaged at -1°c[]. It prefers a mean annual rainfall in the range 1,200 - 2,000mm, but tolerates 600 - 3,000mm[].
Prefers a position with some shade[]. Prefers a well-drained soil, plants are intolerant of water-logging[]. Plants are tolerant of a wide range of soils so long as they are slightly acid[]. This somewhat contradicts the reports that the plant prefers a pH in the range 5.5 - 6.5, tolerating 5 - 8.5[]. Requires a position sheltered from strong winds[]. Plants can tolerate dry periods and some wind if it is not too cold[].
When young, the carambola is delicate and requires careful attention[]. Because it is a fast-growing tree, it requires pruning and thinning of excess fruit at an early stage[].
Flowering continues throughout the year and fruit is available most of the year[].
The fruit can be very variable when plants are grown from seed, with the best forms being large and sweet and others being small and tart[]. Three crops per year can be obtained[].
Seedling varieties should start to crop in 3 - 8 years, whilst selected grafted varieties can start in only 1-2 years[]. Plants can crop prodigiously[], and yields of up to 900 kg/year are common for 10-year-old trees[].
There are many named varieties[].
Some Brazilian cultivars have a very high content of vitamin C as well as an applicable amount of provitamin A[].

Edible Uses

Fruit - raw. The fruit is crisp and juicy with a waxy yellow skin when ripe[]. The best forms are delicious on their own, they also go very well in fruit salads, juiced and mixed with other fruits etc[]. The fruit flavour is enhanced by peeling off the ‘wing’ edges, which removes most of the oxalic acid[]. A quince-like fragrance[]. Plants can produce fruit all year round[]. Fruit quality is variable, though they are normally juicy. Sour forms, and slightly immature fruits, are pickled or made into a relish[]. The orange-yellow fruit is a large, indehiscent berry, 5-8 cm long with a characteristic shape in cross-section resembling a 5-pointed star[]. The fruit is up to 12.5cm x 6cm[].

Flowers - raw[]. An acid flavour, they are added to salads[]. They can also be made into conserves[].

Leaves - raw or cooked[]. An acid flavour, they are used as a sorrel substitute[].

Medicinal

The fruit can be a laxative on account of the oxalic acid it contains[]. It is also used in traditional medicine for skin disorders and fevers[, ]. It is valued by Chinese communities as a remedy for high blood pressure, whilst it is also said to reduce blood sugar levels and so is of help to diabetics[].

The flowers are used to relieve coughs[].

The leaves are used to treat rheumatism[].

The seed is emmenagogue, galactagogue and abortifacient[]. The powdered seed is a good anodyne for treating asthma, colic and jaundice[].

Other Uses

In some countries, the fruit juice is used to remove stains, for example iron rust from linen cloth[]. It can also be used for polishing brass. The fresh juice is an effective stain remover[, ].

Unripe fruits contain potassium oxalate, which is used in dyeing[].

The whitish wood is soft. Generally only available in small dimensions, it is sometimes used for timber in construction and for making small implements, furniture etc[, , ].
The wood is a suitable candidate for firewood[].

Propagation

Seed - sow in a nursery seedbed and transplant into individual containers when large enough to handle. They should be ready to plant out when around 6 - 12 months old[]. The seed has limited viability. Cool temperatures damage the seeds. Viability can be maintained for 6 months with partially dried seeds at 5°c[].
Greenwood cuttings
Budding on to 12 month old seedlings[]
Grafting
Layering. This method can produce fruiting plants within 10 months[].

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