While it cannot be said to rival the mangosteen, the langsat is considered one of the best fruits of the Malayan region.
Like the mangosteen it differs from many other tropical fruits in being juicy and of aromatic subacid flavor, instead of richly sweet. It is doubtless to this characteristic that it owes its popularity among European travelers and residents in the East.
Like several other excellent Malayan fruits, the langsat has not yet become generally cultivated outside of the Asiatic tropics. Its introduction into the western hemisphere has been accomplished, but it is only found as yet in a few botanic gardens and private collections of rare plants.
The tree is erect, symmetrical in form, usually somewhat slender, and attains a height of 35 to 40 feet. Its pinnate leaves are composed of five to seven elliptic-oblong to obovate acuminate leaflets 4 to 8 inches in length. The small subsessile flowers are borne on racemes or spikes arising from the larger branches. The fruit varies in form and character, but is generally oval or round, 1 to 2 inches in diameter, velvety and straw-colored, with a thick leathery skin inclosing five segments of white, translucent, juicy, aromatic flesh, and one to three large seeds. The tree is cultivated in many islands of the Malay Archipelago and in the Philippines. Regarding its importance in the latter region, P. J. Wester writes: "The lanzone is extensively grown for the Manila market in Laguna Province, east of Santa Cruz, and is also cultivated to a considerable extent in Misamis, Zamboanga, the Sulu Archipelago, and around Argao in Cebu." As indicated by Wester's note the common name in the Philippines is lanzone (often spelled lanzori). In the Malay Archipelago the forms lansa and lanseh are sometimes seen, and also the nameayer-ayer.
While it is most commonly eaten out of hand, the culinary uses of the fruit are several. The edible portion is said to contain 1.13 per cent of protein, 1 of acid, and 4.9 of sugar.
Fig. 54. The duku, a variety of the langsat (Lan-sium domesticum) which grows in the Malayan Archipelago. (X 1/7)
In its climatic requirements the plant is distinctly tropical. Wester says: "The lanzone is of vigorous growth and succeeds best under somewhat the same climatic conditions as the mangosteen. It will not grow where there is a pronounced or prolonged dry season, and in the Philippines it is usually grown in half-shade interplanted with the coconut." Experiments indicate that it is not suitable for cultivation in Florida or California, the climate of both states probably being too cold for it. In Cuba and the Isle of Pines it has shown more promise.
Little is known regarding cultural methods, since the lang-sat usually occurs in the Malayan region as a dooryard tree, or along roadsides, where it receives no cultural attention. Propagation is commonly by seeds, which should be planted as soon as possible after they are removed from the fruit; but Wester has shown that cleft- and side-grafting are successful, and one or the other of these methods should be used to propagate choice varieties, and to insure early fruiting. Wester says: "The cion should be well matured but not of old growth, 2 1/2 to 3 1/2 inches long, 1/4 to 3/8 inch in diameter, and inserted in the stock 2 1/2 to 4 inches above ground; when at that height it is 1/4 to 3/8 inch in diameter; cover all wounds with grafting wax. Shield-budding has been done but the percentage of successful buds is small."
The langsat occurs in two distinct forms, one termed langsat and the other duku or doekoe. The typical langsat is borne in clusters of five or six up to twenty or thirty, and the individual fruits are round or oval in form, about an inch long, with a comparatively thin skin. The duku is produced in small clusters of two to five fruits, and is round, from 1 to 2 inches in diameter, with a thicker, darker-colored skin more leathery than that of the langsat.