Speckled Alder
Alnus rugosa

Family: Betulaceae

What it is like

Alnus rugosa is a deciduous Tree growing to 22 m (72ft 2in) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 2. It is in flower in May, and the seeds ripen in October. The species is monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and is pollinated by Wind. It can fix Nitrogen. Suitable for: medium (loamy) and heavy (clay) soils and can grow in heavy clay and nutritionally poor soils. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil.

Height (m): 22

Where it is found

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.

Northern and Eastern N. America - Hudson's Bay to Virginia. Naturalized in C. Europe.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 0

Medicine

Rating: 2

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, 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.

Alterative: Causes a gradual beneficial change in the body, usually through improved nutrition and elimination, without having any marked specific action.

Anodyne: Relieves pain, it is milder than an analgesic.

Astringent: Produces contraction in living tissue, reducing the flow of secretions and discharges of blood, mucus, diarrhoea etc.

Cathartic: A strong laxative but less violent than a purgative.

Emetic: Induces vomiting.

Febrifuge: Reduces fevers.

Odontalgic: Treats toothache (temporary measure only) and other problems of the teeth and gums.

Ophthalmic: Treats eye complaints.

Stomachic: Aids and improves the action of the stomach.

Tonic: Improves general health. Slower acting than a stimulant, it brings steady improvement.

Other

Rating: 3

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. The tree has an extensive root system and can be planted to control banks from erosion. A dark dye is obtained from the bark. Browns, through red to orange colours can be obtained from the bark. The wood is soft, weighing 29lb per cubic foot. The tree is too small to be of importance for lumber or fuel.

Dye: Plants that provide dyes.

Pioneer: Plants, usually trees and shrubs, that can be used to reforest land.

Soil stabilization: Plants that can be grown in places such as sand dunes in order to prevent erosion by wind, water or other agents.

Wood: A list of the trees and shrubs that are noted for having useful wood.

Food Forest: Plants for Edible Forest Gardens and Food Forests.

Nitrogen Fixer: Plants that fix nitrogen in the soil

How it is grown

Prefers a heavy soil and a damp situation. Grows well in heavy clay soils. Tolerates very infertile sites. A fast-growing but short-lived tree. Closely related to A. incana and considered to be no more than a sub-species (A. incana rugosa) by some botanists. 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. For polyculture design as well as the above-ground architecture (form - tree, shrub etc. and size shown above) information on the habit and root pattern is also useful and given here if available. The plant growth habit is multistemmed with multiple stems from the crown. The root pattern is flat with shallow roots forming a plate near the soil surface.

Propagating it: 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.

Best place to grow: Woodland Garden Canopy; Bog Garden;

Habit: Tree

Hardiness: 2-6

Growth: Fast

Soil: Medium, heavy (clay)

Shade: Semi-shade, no shade

Moisture: Moist, wet

Things to keep in mind

Its other names

Local names

Synonyms

A. incana rugosa. (Duroi.)Clausen.