Lansium parasiticum (Osbeck) Sahni & Bennet

An upright slender tree to 12-20 m high. It has sticky sap. The leaves are alternate and simple. Leaves are up to 40 cm long and made up of 5-7 large leaflets. The flowers are yellow in spikes from old wood mostly on the branches. The flowers have 5 petals which join to form a tube. The flowers have a sweet smell. The fruit is 3-5 cm across and divided into 5 segments with 1-2 large seeds. The fruit is borne in long drooping clusters. There can be 25 fruit in a cluster. The fruit is pale yellow when ripe. It develops a brown scurf on the surface as it ripens. The seeds are green and bitter and are not eaten. Langsats have thin skin, milky juice and are oval and 3.7 cm across. Dukus have thick skin, are round, do not have milky juice and are 5 cm across. They are also sweeter than Langsat.

A tropical plant. It suits the hot, wet tropical lowlands. It is native to Malaysia. It occurs in coastal areas and probably up to 700 m altitude in the tropics. A rich deep well drained soil is needed. It suits humid places and is not suited to places with a distinct dry season. It cannot tolerate drought. It can grow with an annual rainfall of less than 1,500 mm. It does well in part shade. It can tolerate lower temperature, rainfall and humidity than rambutan. A temperature between 25°-30°C is best. It grows between 17°N-17°S. A pH between 5.0-6.0 is best.

Fruit is eaten fresh after they fall. They can also be candied, preserved in syrup, or made into wine. Seedless fruit can be bottled in syrup. NOTE The stickiness of the juice of the fruit can be removed by dipping it in boiling water.

Trees are mostly grown by seed. Seeds remain viable for about 5 weeks if kept moist. Seeds should be washed and cleaned before planting. Seeds are planted 1 cm deep in a nursery. Germination takes 1-3 weeks. When seedlings are 15 cm tall they are put into nursery beds for 1-2 years before being planted out in the field. Seedlings do not come into bearing for 12-20 years. They can be grown by budding. Buds should be put onto 4 year old rootstocks of the same species. Buds dry out quickly so should be inserted immediately. Propagation by grafting, marcottage and cuttings is difficult. A spacing of 8-10 m is suitable. Seedlings dry out quickly, so need to be transplanted carefully. Shade is normally provided for the first few years.