Large tree with grey bark. Leaves opposite, pinnate, with 7-9 serrate leaflets. Flowers white, with petals 3-4 mm long, in large branched clusters up to 25 cm across. Fruit a nut, with a long narrow wing 2.5-4 cm long by 3-4 mm wide.
A large deciduous tree. The seedlings need full light, but older trees will withstand shade to some extent; trees planted together with Alnus nepalensis above Pokhara, although outgrown by the A. nepalensis and to some extent suppressed by it, remained healthy. From its altitudinal distribution it must certainly have some tolerance to frost, though this may vary with the provenance; seedlings in the nursery need protection. Although its growth is best on deep moist soils it is said to be one of the species which survive best on difficult sites (Grob, 1982). In parts of the Indian Himalaya it is associated with limestone, but in Nepal it is frequently found on non-calcareous soils. It coppices well.
It grows between 1200 and 2000 m, often in Schima-Castanopsis forest, and also sometimes as an understorey to Pinus roxburghii, where it may be part of a seral stage in the succession to hardwood forest. It is nowhere very abundant in natural forest. It is commonly planted on choutara. Outside Nepal it extends from the Punjab in the west, and to Assam and southwest China in the east.
The winged seeds ripen in September-January and are dispersed by the wind. Naturally dispersed seeds remain dormant through the monsoon after which they have fallen, and germinate in the next year. It was one of the species colonizing neglected plantations at Pipal Chaur in the Kathmandu Valley, although when it was previously planted there it failed. It also colonizes degraded Schima-Castanopsis forest, after protection.
Green seed should be kept moist and sown as soon as possible after collection. It may be sown directly into polypots, with two or three seeds per polypot sown vertically with their wings protruding from the soil. Alternatively it can be sown in beds or trays, and the seedlings pricked out into polypots a few days after they have germinated, before the first true leaves appear. The polypots should contain a mixture of three parts soil to one of sand. Stand-out beds should not be shaded for more than a few days, otherwise growth is retarded and the seedlings may die (Grob, 1982). In many nurseries below 1500 m plants from seed sown in September-October will be ready for planting by the next monsoon, but at higher elevations a further year in the nursery may be needed. The seedlings should be spaced out when they are 20-30 cm tall, and regular root pruning is needed. Plantable seedlings are 25-30 cm tall with root-collar diameters of over 2 mm.
The rate of growth is rather slow to begin with; in trials, trees 18 months old have been between 20 and 30 cm tall, and at 2.5 years about 70 em. In Sankhuwasabha District of eastern Nepal, Sizeland (1986) reports a height of 5 m with 2 cm dbh from trees 4-5 years old planted on a deep fertile loam at 1100-1200 m, but only 1 m at the same age at 1900 m on a fertile loam with Imperata present. In India naturally grown trees had a mean annual diameter increment of 4-6 mm (Gamble, 1922).
If it is to be sown immediately the winged fruit should be collected when it is still green; if it is left until it has turned brown the seed enters a dormant stage and will not germinate until the spring after it has passed through a complete monsoon seal;on. Seed which is to be stored, however, should be collected when it is brown, as it then has a viability of three years, whereas seed collected when green loses its viability quickly. There are about 60,000 winged seeds kg-1. Two nurseries reported the equivalent of 7000 and 3600 plants raised from 1 kg of seed. At lower altitudes germination of green seed is rapid, beginning in 2-4 weeks and being complete within two weeks. At higher altitudes seed sown in September may not germinate until the following March.
It formed about three per cent of the stock of fodder trees, by number, in the area of Dolakha District studied by Robinson and Neupane (1988), but was not a popular tree among farmers, and was not in demand for planting. It was used on a very small scale in the area of Dhading District studied by Upadhyay (1991), but was not recorded in Lamjung by K.P. Gajurel et al. (1987) or in Lalitpur by Upton (1990), though farmers planted over 10,000 trees in the same district between 1985 and 1988 (Hausler, 1990). In general its use in plantations appears to be very local. Many community forestry nurseries do not raise it at all but in Pokhara and Ridi Divisions in 1981 it was the second commonest species planted. Its survival in the plantations of the Community Forestry Project in 1981 and 1982 was 76 per cent, the highest of any important broadleaved species planted. Its main disadvantage is its relatively slow growth.
The wood is white with a light red tinge and weighs about 770 kg m-3. It is hard and tough and is used for ploughs and carrying poles. The tree is lopped for fodder but it is not one of the most important fodder trees. The main season during which it is used is between April and June, after the new leaves have appeared. According to D. Bajracharya et al. (1985) the crude protein content of the leaves is 7.5 per cent. A vigorous tree will produce 100 to 200 kg of fresh leaves in a year.
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