Common Name: Nepalese Alder

General Information

Alnus nepalensis is a fast-growing deciduous or semi-deciduous tree reaching a height of up to 30 metres tall[]. It has a straight bole that is around 60 cm in diameter with occasional specimens up to 2 metres in diameter[].
An excellent agroforestry tree, it is commonly planted to restore land, provide shade for crops, as well as to provide wood for poles, fuel etc[].
This species has a wide distribution. Although some threats have been identified, there are no major range wide threats impacting on the survival of this species, or predicted to in the near future. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

None known

Botanical References

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Range

E. Asia - southern central China, northern India, Nepal, Bangladesh, Myanmar, Thailand, Vietnam.

Habitat

Forests in ravines, on stream banks and occasionally in drier localities, 900 - 2,700 metres in the Himalayas[]. Riverbanks or village margins, often forming pure stands, at elevations of 200 - 2,800 metres in China[].

Properties

Conservation Status	Least Concern
Medicinal Rating
Other Uses Rating
Habit	Semi-deciduous Tree
Height	22.00 m
Growth Rate	Fast
Pollinators	Wind
Cultivation Status	Cultivated, Wild

Cultivation Details

Alnus nepalensis is a plant of the warm temperate to subtropical zones, it can also be grown at higher elevations in tropical areas with high rainfall[, ]. It grows best in areas with a mean annual rainfall ranging from 500 - 2,500mm, and an annual average temperature in the range of 19 - 23°c[]. Mature trees tolerate some frost[]. Plants can withstand a dry season of 4 - 8 months[].
Prefers a heavy soil and a damp situation[, ]. Grows well in heavy clay soils[]. Grows best in deep well-drained loams or loamy soils of alluvial soils, but ranges from gravel to sand to clay[]. Succeeds in very infertile sites[]. Grows well in full light but will also tolerate shade[]. The Nepalese alder is reported to tolerate clay, flooding, fog, gravel, sand, shade, slope, water-logging, and weeds[]. It is not tolerant of high winds[]. Prefers a pH in the range of 6 - 8[].
A fast growing tree, annual increments of 2.7 metres in height and 2.9 cm in diameter have been recorded in Nepal[]. A mean annual diameter increment of 2 cm is common[].
On good sites, poles and fuelwood can be harvested after 5 years[]. Small-diameter timber can be harvested in less than 10 years[]. Longer rotations are needed for ordinary saw timber[].
The tree coppices after cutting, but successful regrowth seems to depend on seasonal and locality variations, with wet season felling and moist localities being best[].
This species has a symbiotic relationship with certain soil micro-organisms, these form nodules on the roots of the plants and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

None known

Medicinal

A useful diuretic for reducing swelling of the leg[].

The juice of the bark is boiled and the gelatinous liquid applied to burns[].

Agroforestry Uses:

The trees develop an extensive lateral root system, fix atmospheric nitrogen, and are fast growing. They are planted to give stability to slopes that tend to slip and erode[]. Their seeds have been broadcast to stabilize landslides area[].
They are effectively used to reforest abandoned taungya areas because they can grow as a pioneer in degraded habitats with low fertility soils[]. They are also planted on the site of mine spoils to reclaim the land[].
Considerable quantities of nutrients are recycled through the leaf litter. Trees may produce 3 - 6 tonnes/ha of leaf litter annually[].
The tree is interplanted with annual crops such as maize, barley, chilli and pumpkin, it is also used as a shade tree for crops such as Cinchona officinalis and Eletaria subulatum[].
A fast growing, pioneer species, it can become established in open, disturbed areas and help to re-established the right conditions for permanent woodland[]. It is suitable for plantation cultivation in tropical uplands[]. The tree is locally cultivated by West Java Forest Service to reforest eroded slopes under ever-wet climates[]. The tree establishes rapidly on areas subject to landslides, binding the soil with its extensive root system and stabilizing the slope[].

Other Uses

The bark contains 7% tannin[], it is used in dyeing and tanning[, , ]. It is used to deepen the red colour of madder, Rubia cordifolia[].

Wood - soft, tough, even grained, rather durable, easily sawn, seasons well and does not warp. It is used to a limited extent in carpentry, house construction, tea boxes, for making furniture, rope bridges etc[, , ]. A very good timber, it deserves to be more widely used[]. In India the trees are coppiced every two years for fuel[].
The wood gives a pulp yield of 47.6%, and bleaching improves the brightness to 76%. It is suitable for the manufacture of high-quality paper[].
The wood has a low calorific value of 18230 kJ/kg. It dries easily, burns well and is an important source of firewood and charcoal[].

Propagation

Seed - best sown in a cold frame as soon as it is ripe and only just covered[]. Spring sown seed should also germinate successfully so long as it is not covered[, ]. The seed should germinate in the spring as the weather warms up. When large enough to handle, prick the seedlings out into individual pots. If growth is sufficient, it is possible to plant them out into their permanent positions in the summer, otherwise keep them in pots outdoors and plant them out in the spring.
If you have sufficient quantity of seed, it can be sown thinly in an outdoor seed bed in the spring[]. The seedlings can either be planted out into their permanent positions in the autumn/winter, or they can be allowed to grow on in the seed bed for a further season before planting them.
Cuttings of mature wood, taken as soon as the leaves fall in autumn, outdoors in sandy soil.