Averrhola Carambola Carambola is a unique, very attractive fruit tree from the Oxalidaceae family. It probably originates in Malaysia and is cultivated in some areas of south-eastern Asia and areas with similar climates all over the world. It is a slowly growing tree o shrub with short, thick trunk and dense crown. It can grow as tall as 6-9 meters and its leaves grow in strange groups from the new branches and young shoots. They can be 15-20cm long with 5-11 smaller, opposite, oval leaves (4-9cm long). Its leaves are very soft and they are closed during then night and face towards the place, where sun will rise. The entire foliage is mostly light green with several dark green spots. Upper side of the leaves is smooth and the lower side of the leaves (or backside) is fuzzy. Flowers grow from the leaf axils and are light purple, 6mm in diameter. They require pollination and the cross-section of fruit looks like a star with 5-6 distinctive arms (6-15cm long and 9cm in diameter). They have a thin, waxy and orange rind that is well attached to the juicy yellow pulp. The fruit is also very aromatic and has excellent, sweet flavor. Sweet Carambolas usually don’t contain more than 4% of sugars and there are only few, 6-12mm long seeds in each individual fruit (if any at all).
Varieties
There are 2 main Carambola fruit types: smaller, very bitter fruit with strong aroma and bigger, sweeter one with pleasant aroma and not many acids. Seeds from the Hawaiian collection were plants in 1935 inUniversity of Florida Agricultural Research and EducationCenter in Homestead. The selection was chosen for further propagation from 1940 to 1950 and these varieties were released to public in 1965 as Golden Star. The first fruit was very big, decorated with many ridges and having an excellent sweet aroma with a hint of sourness. Carambola is fully self-fertile and doesn’t need a pollinator. Some of the cultivars in Tchai-wanu grow in Subtropical research department in Miami, including the Mih Tao variety that was introduced in 1963 under the identification number No 272065. Soon after that new varieties arrived to Florida, such as Dah Pon , Tean Ma and other varieties known only as numbers. Fwang Tung was brought from Thailand by Dr. R J Knight in 1973 and new varieties were bred in there, varieties such as Newcomb, Thayer and Arkin, which are nowadays commercially grown in southern Florida. Some cultivars have flowers with long stylus, some of them have only short stylus.
Climate Carambola is a tropical and subtropical evergreen tree that can withstand light frosts down to -3°C. Trees protected from cold northern winds can survive in the city St. Petersburg, west coast, Florida and Daytona Beach, east coast, Florida. It grows and fruits in Indian mountains up to the elevation 1200 meters above the sea level. It is even cultivated in many Israeli areas, where it adapted to hot and dry winds, although that it need wet climate and lots of water well distributed throughout the year. Carambola has the most delicious fruit in Australian areas, where the annual precipitation is higher than 180cm.
Soil Carambola is not a very demanding tree, it can grow in sand, heavy soils or alkaline soils (but it doesn’t produce very good fruit). It likes very rich and fertile soils with typical water releasing and holding characteristics. It suffers from chlorosis on alkaline soils and need good drainage, because it doesn’t live well in clogged soils.
Propagation Carambola is mainly propagated by seeds, which are able to germinate only a few days. Fully developed seeds should be sown into airy soil and regular watering is necessary. Seeds usually germinate within a week in summer and 14 to 18 days in winter. Young seedlings are usually grown in the containers before they are planted out in the field. They are very tender and sensitive and therefore it is important to give them the best possible care.
Carambola can also be propagated by air layering techniques, but young plants have weak root systems, which is not suitable for planting in the field and therefore is this techniques used only very rarely.
Grafting is successfully used in India, Forket technique in Java and bud grafting in Philippines. Farmers from Java also use the technique of grafting behind the bark of a strong and vigorous rootstock. Large scale production requires that mature, almost red wood is grafted on a Carambola seedling. This technique is used with the best results. The rootstocks should be at least 1 year old and 1-1,5cm thick. Plants grafted on Florida are much younger and both – rootstock and the graft are equally thick (90% success). Grafted Carambolas start producing fruit in 10 months after planting in the field. Older trees can be grafted in the bark.
Cultivation
Carambola requires direct sunlight and they shouldn’t be planted closer than 9 meters from the closest plant. 2.5 and 3 meters high plants are fertilized with 0.5kg fertilizer with N,P,K,Mg ratio 6-6-6-3 around 3 or 4 times a year. In case of Chlrosis infection all plants can be additionally fertilized with Iron, Zinc and Mangan. Leaf fertilizer is advised 4 times a year in areas with alkaline soils and regular irrigation is necessary to have the higherst possible yields. Heavy rains during flowering phase can cause bad pollination and thus small yields. Usually more varieties are planted in one field to achieve the best pollination and highest yields.
Harvest and yields
Carambola fruit ripens in India around September and October, then again in December and January. It fruits all year long in Malaysia and very unpredictably in Florida. The main harvests usually are on the end of the summer and early in winter. Some trees produce fruit in November and December and then again in March and April. Certain areas in the world can see as much as 3 main Carambola fruit harvests a year. Varying weather is important as for higher fruit quality and higher yields. Rip fruit usually falls off the tree, but commercially grown fruit is harvested yellow-green. An average tree can produce as much as 45-120kg a harvest.
Storing Carambola fruit is usually stored in 10 °C and starts rotting after 4 weeks. Fruit kept in 15°C storage room will be fresh only 3 weeks and fruit kept in 21°C storage room will not be fresh after 2 weeks. Waxing prolongs the storage time and also keeps the vitamins in the fruit.
Pests and diseases The worst pests that can attack Carambola in our climate are spider mites and whiteflies. Their liquidation and extermination is very expensive and takes too much time. Here are some pesticides that I found useful: Mospilan, Sumithion, Vetimec, Magus, Nurelle D.
