Common Name: Grey Alder

General Information

Alnus incana is a deciduous, multi-stemmed shrub or (less commonly) a tree that can grow fom 5 - 24 metres tall. It produces suckers around its base[, , ].
The tree is harvested from the wild for local use as a medicine and source of materials. It is a pioneer species, useful when re-establishing native woodland, and is also sometimes grown as an ornamental, particularly forms with incised leaves[].
This species has a very wide distribution and, although it is thought to be sensitive to local extinctions, there are no major threats impacting this species across its full range. It is therefore not considered to be threatened. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

None known

Botanical References

, ,

Range

Europe - Norway to France, through Russia to W Siberia, Greece to Turkey and the Caucasus; N. America - Alaska to Labrador, to California, Virginia

Habitat

Mountains, especially on poor soil[, ]. Wet sandy or gravelly soils, usually along streams and rivers, but also in ponds and swamps[]. It is only found in open sunny areas, being unable to compete in dense shade[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	18.00 m
Growth Rate	Fast
Pollinators	Wind
Cultivation Status	Wild

Cultivation Details

Alnus incana is a very cold-tolerant species, able to grow up to the treeline.
Grows best in a sunny position. Tolerant of a wide range of soils, though it prefers a heavy soil and a damp situation[, , ]. Grows well in heavy clay soils[]. Thrives in drier soils than many other members of this genus[]. Tolerates very infertile sites[]. It grows abundantly in various soil types, from sandy to gravelly, loamy, clayey and mucky, and it can tolerate periods of flooding as well as occasional droughts[].Very tolerant of acid soils, able to stand pH levels of 3.5 - 4.0 without problems[].
A fast-growing species, though short-lived, with trees dying around the age of 60 years[].
The plant coppices easily[].
Towards the northern parts of its range the plant reproduces mainly by suckers[].
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

Catkins - raw or cooked. A bitter taste[].

Medicinal

The speckled alder was quite widely used medicinally by the native North American Indians who used it to treat a variety of complaints[]. It is little used in modern herbalism.
The bark is alterative, astringent, emetic, haemostatic, laxative, ophthalmic, stomachic and tonic[, , , ]. The bark contains salicin[], which probably decomposes into salicylic acid (closely related to aspirin) in the human body[]. This is used as an anodyne and febrifuge[]. The root bark was mixed with molasses and used in the treatment of toothache[]. A decoction of the inner bark was used as a wash for sore eyes[].
The outer bark is astringent and is applied as a poultice to bleeding wounds, it also reduces swellings[].

Agroforestry Uses:

This is an excellent pioneer species for re-establishing woodlands on disused farmland, difficult sites etc[]. It quickly invades gaps created by fire and logging in native wetland forests[]. 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[].
The tree has an extensive root system and can be planted to control banks from erosion[].
This species fixes atmospheric nitrogen and is also tolerant of polluted soils, it can be used for land reclamation, especially on coal tips[].

Other Uses

The bark and the fruits contain up to 20% tannin[, , ]. The bark and the strobils are a source of tannin[]. A dark dye is obtained from the bark[]. The colour can range from orange through red to brown[].

The bark is rich in tannin; it also contains alnulin and alniresinol[].
The wood contains the resin 'xylan'[].

The wood is light in weight, soft, straight-grained, easy to split, very durable in water[]. It is lighter -coloured and firmer than that of black alder. It is used for carpentry, turnery, making clogs, bowls, woodcuts etc.[]. Much valued by cabinet makers[, ]. It has no commercial value[].
This species is used locally for fuel[, ], and provides the best charcoal for drawing[].

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.