Mountain Alder (Alnus tenuifolia)
At a glance
- Lifecycle
- Perennial (hardy)
- Exposure
- Full sun
- Frost limit
- −45.6 °C
Cultivation
Prefers a heavy soil and a damp situation. A fast-growing but short-lived tree. There is some confusion over the correct name of this tree with one authority citing the European species A. incana as the correct name. Some modern works treat it as a subspecies (Alnus incana tenuifolia). 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.
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[200, K]. 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.
Edible uses
Catkins - raw or cooked. A bitter taste.
Medicinal uses
The bark is astringent, emetic, haemostatic, stomachic and tonic. The outer bark is astringent and is applied as a poultice to bleeding wounds, it also reduces swellings.
Material uses
This is an excellent pioneer species for re-establishing woodlands on disused farmland, difficult sites etc. Its fast rate of growth means that it quickly provides sheltered conditions to allow more permanent woodland trees to become established. In addition, bacteria on the roots fix atmospheric nitrogen - whilst this enables the tree to grow well in quite poor soils it also makes some of this nitrogen available to other plants growing nearby. Alder trees also have a heavy leaf canopy and when the leaves fall in the autumn they help to build up the humus content of the soil. Alder seedlings do not compete well in shady woodland conditions and so this species gradually dies out as the other trees become established[K]. The tree has an extensive root system and can be planted to control banks from erosion. The bark and the strobils are a source of tannin. Wood - soft, straight-grained, very durable in water.
Habitat
Moist soils by swamps, streams, ponds and lakes in foothills to well up in the mountains.
Native range
Western N. America - Alaska to California and New Mexico.