Common Name: Red Alder

General Information

Alnus rubra is a deciduous tree, often with several trunks; the crown is narrow or pyramidal; it can grow up to 30 metres tall. The bole can be up to 90cm in diameter[, , ].
The tree is harvested from the wild for local use as a food, medicine and source of materials. Alnus rubra is considered to be the most important commercial hardwood of the Pacific Northwest[].
Alnus rubra is a commonly occurring species in North America. There are no known threats that are or will adversely affect this species in the foreseeable future. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

The freshly harvested inner bark is emetic but is alright once it has been dried[].

Botanical References

, ,

Range

Western N. America - Alaska, south to California.

Habitat

Moist rich soils in woods below 600 metres and within 50 km of the coast[, , ]. Mainly restricted to streams and wet areas before European settlement, logging etc has provided an abundance of open sites favouring colonization by this plant[]

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Tree
Height	20.00 m
Growth Rate	Fast
Pollinators	Wind
Cultivation Status	Wild

Cultivation Details

Prefers a heavy soil and a damp situation[, ]. Grows well in heavy clay soils[]. Tolerates very infertile sites[]. A very wind resistant tree with excellent establishment in severely exposed sites, it tolerates severe maritime exposure[, ].
The red alder is a very fast growing tree, even when planted in severe exposure[, , ], but it is short-lived, dying when 60 - 80 years old[]. Trees that are 5 years old from seed have reached 6 metres in height on a very exposed site in Cornwall, they are showing no signs of wind-shaping[]. This is an important pioneer tree, quickly invading logged or burnt over sites, and providing ideal conditions for other trees to become established[, ].
A very ornamental tree[].
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[]. Red alder has been estimated to fix as much as 300 kg of nitrogen per hectare[].

Edible Uses

Catkins - raw or cooked. They are rich in protein but have a bitter flavour and are not very palatable[].

Inner bark - cooked, It must be dried since it is emetic when fresh[, , ]. No more details are given but inner bark is often dried, ground into a powder and then used as a thickening in soups etc or mixed with cereals when making bread[].

Sap - raw[]. Harvested in late winter, the flow is best on a warm, sunny day that follows a cold frosty night. A sweet flavour, it was often used to sweeten other foods[].

Buds[, ]. No further information is given, does this refer to the flower buds or leaf buds?[]

Medicinal

Red alder was widely employed medicinally by native North American Indians who mainly used the bark to treat a wide range of complaints[]. The plant is little used in modern herbalism[].
The bark is anodyne, appetizer, astringent, cathartic, cytostatic, emetic, febrifuge, stomachic and tonic[, , , ]. An infusion of the bark has been used in the treatment of many complaints such as headaches, rheumatic pains, internal injuries and diarrhoea[, ]. Externally, a poultice of the bark has been applied to eczema, sores and aches[].
The sap is applied externally to cuts[].
The catkins and young cones are astringent and have been chewed in the treatment of diarrhoea[].

The plant is used in homeopathy where it has some reputation as a remedy for skin affections, glandular enlargements and indigestion from imperfect secretion of gastric juice[].

Clinical studies have verified that this species contains betulina and lupeol, compounds shown to be effective against a variety of tumours[].
The bark contains salicin[], which probably decomposes into salicylic acid (closely related to aspirin) in the human body[]. This has been shown to be antiinflammatory, anodyne and febrifuge[].

Agroforestry Uses:

A fast-growing and very wind resistant tree, it is an excellent species for providing rapidly produced shelterbelts[].
The trees extensive root system also makes it suitable for controlling erosion along the banks of rivers and on steep slopes[, ]. It is used in forested riparian buffers to help reduce stream bank erosion, protect water quality and enhance aquatic environments[].
This is an excellent pioneer species for re-establishing woodlands in open spaces such as disused farmland, deforested slopes, 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 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[].

Other Uses

Tannin is obtained from the bark and the strobils[].
A red to brown dye is obtained from the bark[, , ].

Both the roots and the young shoots have been used in making baskets[].

The heartwood is light brown, tinged with red; it is clearly demarcated from the thick band of nearly white sapwood. The texture is fine and even; the grain straight and close. The wood is light in weight, soft, brittle, not strong, very durable in water. It is easy to work; sands and polishes easily; holds paints and coatings well; stains readily; and seldom splits. When stained it makes a good imitation mahogany[, ]. Due to these favourable characteristics, and the fact that it is much less expensive than other hardwoods used in furniture manufacturing, the wood is used extensively for furniture making and cabinetry. It is also used in the manufacture of novelties, trim, panelling, pallets, veneers, plywoods and paper roll plugs. Smaller manufactured items include brush handles, spools, trays, shoe soles and boxes[, , , , , ].
The wood is an important source of pulp for paper products[].
An important source of firewood, it makes a good fuel that does not spark and so can be used in the open[, , , ]. The wood is used to make a high grade 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.