The seedlings are said to stand frost moderately well. The tree is fairly tolerant to low soil fertility, but will not grow on very poor, rocky sites.
Probably indigenous in Nepal between 1000 and 1200 m, but it has been widely planted, both in Nepal and many other countries of tropical Asia.
The seed ripens between September and February. It can often be obtained from places where people wash clothes, as it is discarded after the pulp has been removed as a soap substitute. There are 600-900 seeds kg-1. It can be stored for a year. Before the seed is sown it should be put in hot water, and left in it for seven days; if this is not done, germination may be greatly delayed. Also seed sown in autumn will usually not germinate until the following spring. Treated seed sown in February-March will usually germinate within 4-6 weeks. Untreated seed takes 2-4 months to germinate, and germination is very irregular. Germination percentage is usually good; the average number of plants produced from eight nurseries in 1982 was 360 from one kilogram of seed, with some nurseries producing 600.
The seed should be sown directly into polypot, with one or two seeds per container. Seed sown in February-March will provide plantable stock by the rains. Very frequent root pruning is essential; once a strong taproot has been allowed to develop outside the plastic pot, pruning the root is likely to kill the plant.
It was reported by Thunberg and Werner (1981) that bare-root plants had been used successfully in Ilam District. However a later report from Ilam (Olsson, 1983) does not confirm this; only 29 per cent of the trees planted 1981-1982 survived, though it is not stated how many of these, if any, were from bare-root stock. In Darchula District, in the far west, Wilson (1988) reports that bare-root plants could be used if planted in winter when they were dormant, but in general survival of bare-root plants was only 30 to 50 per cent. She also says that stumps could be used. Troup (1921) states that stumps from two-year-old seedlings can be used for planting, though a certain amount of mortality may be expected. He also reports that propagation by cuttings is possible. Growth in plantations is reported to be slow and survival has often been poor. For the planting years 1981 and 1982 the Community Forestry Development Project reported a survival rate in plantations of only 27 percent, and in farmers' private plantings of 43 percent (J.G. Campbell and Bhattarai, 1983). This suggests that it has often been planted on unsuitable sites. For fruit production wide spacing should be used.
Its main use is for its fruits, the pulp of which is used in place of soap for washing clothing. It is also used medicinally as an expectorant and in the treatment of epilepsy, and as a fish poison. According to the Department of Medicinal Plants (1970) about 4000 maund of the fruit (approximately 150 t) are exported annually from Nepal. The wood weighs about 700 kg m-3 but is little used, presumably because of the value of the tree for its fruits. The leaves are occasionally used for fodder, but according to R.V. Singh (1982) this is of poor quality. It is not included in Panday's (1982) list of fodder trees.
Because of the value of the fruits as a soap substitute some people are prepared to plant the tree. However the ease of obtaining the seeds, and of growing plants in the nursery, have resulted in Sapindus having been raised on a larger scale than is probably justified, especially in view of its relatively poor performance in plantations. It is more suitable for individual farmers to plant near their houses, than as a plantation tree.