Grey Alder (Alnus incana) — Practical Plants

Uses

Toxicity

Toxicity warning. The historical record reports a hazard for this plant. Do not use it to decide which parts are safe to eat or use medicinally.

None known

None known There are no edible uses listed for Alnus incana.

Medicinal uses

Historical medicinal uses. These records describe reported uses. They do not establish safety or effectiveness. Ask a qualified health professional before using any plant medicinally.

None known

Material uses

This species fixes atmospheric nitrogen and is also tolerant of polluted soils, it can be used for land reclamation, especially on coal tips^[4]. 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 bark and the fruits contain up to 20% tannin^[6]^[8]^[5]. Wood - light, soft, fairly elastic, easy to split. Used for clogs, bowls, woodcuts etc. Much valued by cabinet makers^[6]^[8].

Product or use: Tannin

Product or use: Wood

Environment

Range

Europe. Introduced in Britain^[3].

Habitat

Mountains, especially on poor soil^[3]^[7].

Light

full sun

Shade tolerance

light shade

Water

high

Hardiness

Zone 2+

Soil textures

loamy, clay, heavy clay

Soil pH

acid, neutral, alkaline

Tolerances

high wind, maritime exposure

Wind

Yes

Maritime

Yes

Tolerates Nutritionally Poor Soil

Drought

intolerant

Propagation

Seed - best sown in a cold frame as soon as it is ripe and only just covered^[4]. 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^[9]. 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.

Cultivation

Prefers a heavy soil and a damp situation^[1]^[2]. Grows well in heavy clay soils^[2]. Thrives in drier soils than many other members of this genus^[4]. Tolerates very infertile sites^[4]. 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^[4].

References

F. Chittendon. RHS Dictionary of Plants plus Supplement. 1956 Oxford University Press 1951-00-00

↩

Bean. W. Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement. Murray 1981-00-00

↩1 ↩2

Clapham, Tootin and Warburg. Flora of the British Isles. Cambridge University Press 1962-00-00

↩1 ↩2

Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press 1992-00-00 ISBN 0-333-47494-5

↩1 ↩2 ↩3 ↩4 ↩5

Rottsieper. E.H.W. Vegetable Tannins The Forestal Land, Timber and Railways Co. Ltd. 1946-00-00

↩

Uphof. J. C. Th. Dictionary of Economic Plants. Weinheim 1959-00-00