Lansium domesticum

Cultivation Details

Langsat is an ultra-tropical plant^[1]. It is a tree of tropical lowland forest and even in its native range it cannot be grown at elevations above 650 - 750 metres^[1]. The temperature range for growth is reported to be 12 - 40°c with the optimum between 20 - 35°c^[1]. It needs a humid atmosphere, plenty of moisture and will not tolerate long dry seasons^[1]. The annual rainfall range for growth is reported to be 1,000 - 3,000mm with the optimum between 1,400 - 2,200mm^[1]. It can cope with a dry season, if shade and moisture supply are adequate^[1]. In Java, for example, the tree grows in areas with 6 - 12 wet months if there is over 100 mm rainfall monthly^[1]. Young plants require shade from strong sun, but older plants can tolerate full sun, though some shade is still beneficial^[2]. Grows best in a slightly acid, humus-rich, well-drained, fertile soil^{[2, 3]}. Dislikes heavy soils^[3]. Prefers a pH in the range 6 - 6.5, tolerating 5.5 - 7.5^[4]. The trees are shallow rooted and greatly benefit from a thick layer of organic matter to protect their numerous feeding roots^[5]. A slow-growing plant, the seedlings take 12 - 20 years before they bear their first crop, whilst grafted trees can beging cropping within 5 - 6 years^{[1, 2, 5]}. Trees do not always grow and fruit well outside Asia. There are successful commercial orchards in Surinam, though the plant has been unfruitful in Honduras. It succeeds in Trinidad and Puerto Rico^[1]. In the Philippines, a productive tree averages 1,000 fruits per year, where it is grown in half shade interplanted with coconut^[1]. There are two distinct botanical varieties in the Malay Peninsula, with a third form grown in Java:- 'Pubescens' is the typical wild langsat which is a rather slender, open tree with hairy branchlets and nearly round, thick-skinned fruits having much milky latex. Although often referred to as the wild type, it is commonly cultivated and shows considerable range of form, size and quality^[1]. The fruit spikes are long, carrying 15 - 25 ovoid, thin-skinned fruits which exude latex until fully ripe. The taste is generally (sub)acid and refreshing. Langsat is adapted to more seasonal climates further from the equator than the following form^[5]. 'Domesticum', often called the duku, doekoe, or dookoo, is a more robust tree, broad-topped and densely foliaged with conspicuously-veined leaflets; the fruits, borne few to a cluster, are oblong-ovoid or ellipsoid, with thin, brownish skin, only faintly aromatic and containing little or no milky latex^[1]. Duku bears shorter fruit spikes, usually with few fruits. Generally sweet and aromatic, the fruits are normally larger and more rounded than the langsat fruit, with a thick skin (up to 6 mm) and relatively free from latex. The trees appear to be more suited to the humid tropics^[5]. 'Kokossan' is a form found mainly in Java - its trees have the largest flowers and most pubescent leaves. The globose, orange yellow fruits are smaller, they have a tough pericarp and contain latex. The seeds are not removed when eating the fruit - instead a hole is bitten into the skin and the juice sucked out^[6]. There are desirable types in each group. Some small fruits are completely seedless and fairly sweet^[1]. The plant commonly sets fruit (and seed) without prior fertilization (parthenocarpic)^[5].