langsat

''Lansium parasiticum'', commonly known as langsat (), lanzones (), or longkong in English; duku in Indonesian or dokong in Terengganu Malay, is a species of tree in the Mahogany family with commercially cultivated edible fruits. The species is native to Southeast Asia.

Description

The tree is average sized, reaching in height and in diameter. 30 years old trees grown from seed and planted at 8 × 8 meter spacing can have a height of 10 meters and diameter of 25 cm. The trunk grows in an irregular manner, with its buttress roots showing above ground. The tree's bark is a greyish colour, with light and dark spots. Its resin is thick and milk coloured.

The pinnately compound leaves are odd numbered, with thin hair, and 6 to 9 buds at intervals. The buds are long and elliptical, approximately by in size. The upper edge shines, and the leaves themselves have pointed bases and tips. The stems of the buds measure .

The flowers are located in inflorescences that grow and hang from large branches or the trunk; the bunches may number up to 5 in one place. They are often branched at their base, measure in size, and have short fur. The flowers are small, with short stems, and have two genders. The sheathe is shaped like a five lobed cup and is coloured a greenish-yellow. The corona is egg-shaped and hard, measuring by . There is one stamen, measuring in length. The top of the stamen is round. The pistil is short and thick.

The fruit can be elliptical, ovoid or round, measuring by in size. Fruits look much like small potatoes and are borne in clusters similar to grapes. The larger fruits are on the variety known as duku. It is covered by thin, yellow hair giving a slightly fuzzy aspect. The skin thickness varies with the varieties, from to approximately . With the skin removed, the fruit resembles peeled garlic in appearance, with half a dozen white, translucent lobes, some of which contain a flat, bitter tasting seed. The seeds are covered with a thick, clear-white aril that tastes sweet and sour. The taste has been likened to a combination of grape and grapefruit and is considered excellent by most. The sweet juicy flesh contains sucrose, fructose, and glucose. For consumption, cultivars with small or undeveloped seeds and thick aril are preferred.

Cultivars

There are numerous cultivars of ''L. parasiticum''. Overall, there are two main groups of cultivars, those named ''duku'' and those named ''langsat''. There are also mixed duku-langsat varieties.

Those called duku generally have a large crown, thick with bright green leaves, with short bunches of few fruit. The individual fruit are large, generally round, and have somewhat thick skin that does not release sap when cooked. The seeds are small, with thick flesh, a sweet scent, and a sweet or sour taste.

Meanwhile, the variant commonly known as langsat generally has thinner trees, with a less dense crown consisting of dark green leaves and stiff branches. The bunches are longer, and each bunch holds between 15 and 25 large, egg-shaped fruit. The skin is thin and releases a white sap when cooked. The flesh is watery and tastes sweet and sour.

''Lansium domesticum'' var. ''aquaeum'' is distinguished by its hairy leaves, as well as the tightly packed dark yellow fruit on its bunches. The fruit tends to be small, with thin skin and little sap; the skin is difficult to remove. To be eaten, the fruit is bitten and the flesh sucked through the hole created, or rubbed until the skin breaks and the seeds are retrieved. In Indonesia the fruit has several names, including ''kokosan'', ''pisitan'', ''pijetan'', and ''bijitan''. The seeds are relatively large, with thin, sour flesh.

Reproduction

The seeds of ''L. parasiticum'' are polyembryonic, the multiple embryos resulting from apomixis.

''Lansium parasiticum'' is traditionally reproduced by spreading seedlings, either cultivated or collected from below the tree. It has been said that new seedlings require 20 to 25 years to bear fruit, with the possibility of the quality being inferior. However other sources quote 12 years to first production from seed and no variations. Production often varies from year to year, and depends to some extent on having a dry period to induce flowering. One example of ten trees in Costa Rica about twenty-five years old produced during five years the following weights of salable fruits: 2008: 50 kilos, 2009: 2000 kilos, 2010: 1000 kilos, 2011: 100 kilos, 2012: 1500 kilos. Experiments in the Philippines with grafting where two trees are planted close to each other and then grafted when one to two meters tall to leave twin root systems on a single main trunk have resulted in earlier and less erratic fruit production.

Another common method is by air layering. Although the process requires up to several months, the new rooted tree produced is itself ready to bear fruit within two years. Trees cultivated with this method have a high death rate, and the growths are less resilient.

The third common way to reproduce ''L. parasiticum'' is with grafting. This results in the new trees having the same genetic characteristics as their parent, and being ready to bear fruit within 5 to 6 years. The offspring are relatively stronger than transplanted shoots.

Ecology

''Lansium parasiticum'' grows well in mixed agroforests. The plant, especially the ''duku'' variant, prefers damp, shaded areas. It can be grown in the same agroforest as durian, petai, and jengkol, as well as wood-producing trees.

''Lansium parasiticum'' is grown from low grounds up to heights of above sea level, in areas with an average rainfall of a year. The plant can grow and blossom in latosol, yellow podzol, and alluvium. The plant prefers slightly acidic soil with good drainage and rich in mulch. The ''langsat'' variant is hardier, and can weather dry seasons with a little shade and water. The plant cannot handle floods.

''Lansium parasiticum'' generally bears fruit once a year. This period can vary between areas, but blooming is generally after the beginning of the rainy season and fruit production some four months later.

Distribution

''Lansium parasiticum'' is native to the Malesian phytochorion of Southeast Asia, from Peninsular Thailand and Peninsular Malaysia, to Java, Sumatra, Borneo, the Philippines (Luzon, Camiguin, Basilan, and