Despite its occurrence in some types of evergreen forest, it is deciduous; it grows up to 50 m tall by 1 m in diameter. In youth it is moderately shade-tolerant and young plants need protection from strong sun; older trees need full light. It grows best on well-drained, deep, rich, loamy soils, and on dry hill slopes the growth is stunted. Indeed it is a demanding species, and should only be planted on fertile sites. The seedlings are frost-hardy. The tree is sensitive to fire and will not withstand much drought. Seedlings are readily browsed. One of its major drawbacks is its susceptibility to damage by shoot borer (Hypsipyla robusta).
It is found in Nepal from the Terai up to about 1700 m, mainly in forests near rivers and in moist localities. It is a characteristic species of Stainton's (1972) Tropical Evergreen Forest, Subtropical Evergreen Forest, and Subtropical Semi-evergreen Forest, but,also occurs in other forest types.
The seed, which is produced in copious amounts, falls after the early pre-monsoon rains or during the early monsoon. It is distributed by wind, but seed on the ground is carried by the water from the heavy rains until it lodges under bushes, walls, or similar obstacles. If there are breaks in the early rains the seed may germinate and subsequently die, but usually a good proportion of it germinates at a suitable time. Regeneration is good on deep, sandy, loam soils near rivers, and on abandoned cultivation. It can be increased by clearing the ground near seed bearers.
The light, winged seeds are contained in capsules which ripen between April and June. The capsules must be collected from the tree before they open and scatter the seed, which is dispersed over large distances by the wind. As the tree tends to have a straight, tall, branchless stem, climbing it to collect seed is rather difficult. There are between 125,000 and 589,000 seeds kg-1, the average being about 350,000. Published accounts on its viability vary; it has been recorded that dry seed can be stored for a year in sealed tins, but other sources report 50 per cent loss of viability in ten weeks. The discrepancies may be due to different storage methods. As there are uncertainties about the storage life of the seed, it is better to sow it in the early monsoon, that is within three months of the date of collection.
It should be sown in beds or trays under shade and treated like that of Alnus nepalensis. When the seedlings are about 5 cm tall, they should be pricked out, either into polythene pots or, for raising stumps, into beds at a spacing of about 20 cm x 20 cm. Either method should produce plantable stock by the next monsoon.
The stem borer Hypsipyla robusta is a serious pest. No reports of damage by this insect have yet been recorded from Nepal, but as it occurs almost throughout the Old World tropics where trees of the family Meliaceae are found, it is unlikely that it will not occur here also. Hypsipyla is a moth. of which the larvae tunnel along the centre of young twigs. and under the bark of older trees. When the twigs are attacked the portion above the point of attack dies, and, if the tree survives, repeated dying back of the shoots eventually produces a very branchy misshapen tree of little value for timber. In addition to the shoot dieback, the presence of borer can be recognized by a gummy exudation near the point of attack. If the attack is recognized at an early stage some control is possible by cutting off the infested shoots and burning them, but recolonization by insects from the natural forest is always likely. The best way of avoiding attack is not to plant T. ciliata in large pure blocks in areas where Hypsipyla is present. If T. ciliata is planted in single lines in a plantation of other species, or under the shade of natural forest, attack is less likely.
Under favourable site conditions. and where there is no stem borer attack, growth is rapid. No data are available from Nepal. but in Assam trees 22 years old had an average height of 19.2 m and an average diameter of 18 cm. Volume and biomass tables and equations are available in E.R. Sharma and Pukkala (1990a; 1990b).
Toona ciliata is a moderately hard, fairly light, easily worked and moderately durable timber. The heartwood is light brick red to reddish-brown. It is used for furniture, interior boards, planks, carvings, and cigar boxes. In parts of Nepal, however, its use inside houses is avoided for religious reasons. It weighs about 560 kg m-3; the calorific value of the sapwood is 21,700 kJ kg-1 , and that of the heartwood 21,400 kJ kg-1. The leaves contain about 15 per cent crude protein, and are lopped for fodder when they are available. It is not, however, an important fodder tree in most areas. In Lalitpur District it was used to a small extent, in April, on southern slopes below 1250 m altitude (Upton, 1990).
It has been planted on a fairly large scale in community plantations, and by private farmers, in some parts of Nepal (Mader and Stewart, 1983). In Pokhara there was 75 per cent survival in March from trees planted in the previous monsoon (Grob, 1982), but the overall rate of survival was considerably lower. 43 per cent in 1983/84 according to Ghimire and Nielsen (1985). It has a number of disadvantages. It only grows really well on moist fertile sites; the seed is rather difficult to collect; the largely superficial, root system means that it should not be planted close to agricultural crops; and there are dangers of attack by shoot borer. For the time being only small-scale trials are recommended, especially of pure plantations.