It is a close relative of the carambola tree.
Averrhoa bilimbi is a small tropical tree native to Malaysia and Indonesia, reaching up to 15m in height. It is often multitrunked, quickly dividing into ramifications. Bilimbi leaves are alternate, pinnate, measuring approximately 30–60 cm in length. Each leaf contains 11-37 leaflets; ovate to oblong, 2–10 cm long and 1–2 cm wide and cluster at branch extremities. The leaves are quite similar to those of the Otaheite gooseberry. The tree is cauliflorous with 18–68 flowers in panicles that form on the trunk and other branches. The flowers are heterotristylous, borne in a pendulous panicle inflorescence. There flower is fragrant, corolla of 5 petals 10–30 mm long, yellowish green to reddish purple. The fruit is ellipsoidal, elongated, measuring about 4 – 10 cm and sometimes faintly 5-angled. The skin, smooth to slightly bumpy, thin and waxy turning from light green to yellowish-green when ripe. The flesh is crisp and the juice is sour and extremely acidic and therefore not typically consumed as fresh fruit by itself. Fruit is often preserved and used as a popular flavouring/seasoning and is a key ingredient in many Indonesian dishes such as sambal belimbing wuluh and asam sunti (see Culinary interest). A. bilimbi holds great value in complementary medicine (see Medical interest) as evidenced by the substantial amount of research on it. According to traditional Indonesian/Malaysian knowledge, the trunk and branches of tree require exposure to sunlight to initiate flowering/fruiting, which can be assisted by removing leaves from the inner canopy.
Possibly originated in Moluccas, Indonesia, the species is now cultivated and found throughout Indonesia, the Philippines, Sri Lanka, Bangladesh, Maldives, Myanmar (Burma) and Malaysia. It is also common in other Southeast Asian countries. In India, where it is usually found in gardens, the bilimbi has gone wild in the warmest regions of the country. It is also seen in coastal regions of South India.
Outside of Asia, the tree is cultivated in Zanzibar. In 1793, the bilimbi was introduced to Jamaica from Timor and after several years, was cultivated throughout Central and South America where it is known as mimbro. In Suriname this fruit is known as lange birambi. Introduced to Queensland at the end of the 19th century, it has been grown commercially in the region since that time. In Guyana, it is called Sourie, One finger, Bilimbi and Kamranga.
This is essentially a tropical tree, less resistant to cold than the carambola, growing best in rich and well-drained soil (but also stands limestone and sand). It prefers evenly distributed rainfall throughout the year, but with a 2- to 3-month dry season. Therefore, the species is not found, for example, in the wettest part of Malaysia. In Florida, where it is an occasional curiosity, the tree needs protection from wind and cold.
In Indonesia, A. bilimbi, locally known as belimbing wuluh, is often used to give sour or an acidic flavor to food, substituting tamarind or tomato. In the north western province of Aceh, it is preserved by salting and sun-drying to make asam sunti, a kitchen seasoning to make a variety of Achenese dishes.
In the Philippines, where it is commonly found in backyards, the fruits are eaten either raw or dipped in rock salt. It can be either curried or added as a souring agent for common Filipino dishes such as sinigang, pinangat and paksiw. It is being sun-dried for preservation. It is also used to make salad mixed with tomatoes, chopped onions with soy sauce as dressing.
In Kerala and Bhatkal, India, it is used for making pickles and to make fish curry, especially with Sardines, while around Karnataka, Maharashtra and Goa the fruit is commonly eaten raw with salt and spice. In Guyana and Mauritius, it is made into achars/pickles too.
In Seychelles, it is often used as an ingredient to give a tangy flavor to many Seychellois creole dishes, especially fish dishes. It is often used in grilled fish and also (almost always) in a shark meat dish, called satini reken. It is also cooked down with onion, tomato, and chili peppers to make a sauce. Sometimes they are cured with salt to be used when they are out of season.
In the Philippines, the leaves serve as a paste on itches, swelling, rheumatism, mumps or skin eruptions. Elsewhere, they are used for bites of venomous creatures. A leaf infusion is used as an after-birth tonic, while the flower infusion is used for thrush, cold, and cough. Malaysians use fermented or fresh bilimbi leaves to treat venereal diseases. In French Guiana, syrup made from the fruit is used to treat inflammatory conditions. To date there is no scientific evidence to confirm effectiveness for such uses.
In some villages in the Thiruvananthapuram district of India, the fruit of the bilimbi was used in folk medicine to control obesity. This led to further studies on its antihyperlipidemic properties.
The fruit contains high levels of oxalate. Acute kidney failure due to tubular necrosis caused by oxalate has been recorded in several people who drank the concentrated juice on continuous days as treatment for high cholesterol.