Red Alder – Fagales Betulaceae Alnus rubra

Identification & Description:
Red Alder is a fast growing tree reaching up to 80 feet in height. The bark is smooth, thin and gray often covered with moss and lichen. The leaves are sharp pointed with wavy, margins with blunt teeth. The flowers appear before the leaves with male and female plants producing hanging catkins with the male being 2 – 5 inches in length and the female a little less than an inch. The fruit is a small brownish cone that stays on the tree over the winter. Red Alder grows in moist woods near streams, floodplains, slides and roadsides, just about anywhere moist soils are found. It grows well in both sun and semi shaded areas.

A stand of lichen-covered Alnus rubra, Red alder, is a remarkable sight. Peering through a stand, you can almost see the creatures that artists hide in their paintings of white barked trees and snow. Because alders are such a common tree in the western portion of the Pacific Northwest, they are often thought of as weed trees. I have thought this, too, as I pull the numerous seedlings that volunteer in my ornamental gardens or very close to the fruit trees. However, when I see a mature stand of Red alder, those thoughts quickly disappear. They are important trees for many reasons.

Alders fix nitrogen into the soil–well not exactly. A bacterium called actinomycete invades the alder’s roots, where it draws nitrogen from the air and fixes it to the nodules that have formed. If you ever pull up an alder seedling, you can see the orange-red colored nodules all over the roots. In our Northwest soil, this is a great way to get the nitrogen, that our rains wash away, back into the soil. A stand of red alder can provide up to 705 pounds (320 kg) of nitrogen every year! This helps the tree to grow over places like avalanche tracks, flood plains and other disturbed areas, such as where logging has occurred. Alder helps provide the nitrogen for younger conifer seedlings growing up under the protection of their canopy. The alders start to decline after about 50 years, giving way to the next generation of forest trees.

Physical Characteristics
A decidious tree growing to 80 feet at a fast rate. It is hardy to zone 6. It is in flower in March, and the seeds ripen from September to October. The flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and are pollinated by Wind. It can fix Nitrogen. We rate it 4 out of 5 for usefulness.
The plant prefers medium (loamy) and heavy (clay) soils and can grow in heavy clay and nutritionally poor soils. The plant prefers acid, neutral and basic (alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It requires moist or wet soil. The plant can tolerate maritime exposure.

Unique Features:
• In the forest, the tree develops a slightly tapered trunk with a narrow, rounded crown, in the open it has a broad cone shape with the crown starting near the trunk
• Is BC’s most important hardwood
• While all other alders are only shrubs, the red alder is a large coastal tree
• Puts nitrogen back into the soil
• Fast growing but only lives 40 to 60 years

Edible Uses
Flowers; Inner bark; Sap.
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[K].

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?

Other Uses
• Modern – furniture, flooring, firewood

• Traditional – bark: dying basket material, fish nets, wood, wool, feathers as well as human hair and skin (colours ranged from black and brown to orangey-red; inner bark sometimes used for food; wood: carving bowls, spoons and platters, smoking meat, firewood

Charcoal; Dye; Fuel; Pioneer; Shelterbelt; Soil stabilization; Tannin; Wood.
A fast-growing and very wind resistant tree, it is an excellent plant for providing rapidly produced shelterbelts. The trees extensive root system also makes it suitable for controlling erosion along the banks of rivers.

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.

Tannin is obtained from the bark and the strobils.

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

A red to brown dye is obtained from the bark.

Wood – soft, brittle, not strong, light, close and straight-grained, very durable in water. An important lumber tree, it makes a good imitation mahogany and is used for cheap furniture etc. A good fuel, it does not spark so can be used in the open, it also makes a high grade charcoal.

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

Native Range
Red alder is most often observed as a lowland species along the northern Pacific coast. Its range extends from southern California (lat. 34° N.) to southeastern Alaska (60° N.). Red alder is generally found within 200 km (125 mi) of the ocean and at elevations below 750 m (2,400 ft). It seldom grows east of the Cascade Range in Oregon and Washington or the Sierra Nevada in California, although several isolated populations exist in northern Idaho.

Red alder grows in climates varying from humid to superhumid. Annual precipitation ranges from 400 to 5600 mm (16 to 220 in); most of the precipitation is rain in winter. Summers are generally cool and dry. Temperature extremes range from -30° C (-22° F) in Alaska and Idaho to 46° C (115° F) in California. Low winter temperatures and lack of precipitation during the growing season appear to be the main limits to the range of red alder. For good development of trees, either annual precipitation should exceed 630 mm (25 in) or tree roots should have access to ground water.

Solis and Topography
Red alder is found on a wide range of soils, from well-drained gravels or sands to poorly drained clays or organic soils. It grows primarily on soils of the orders Inceptisols and Entisols but is also found on some Alfisols, Ultisols, and Histosols. Best stands are found on deep, well-drained loams or sandy loams of alluvial origin; however, some excellent stands are also found on residual or colluvial soils derived from volcanic materials.

Soil moisture during the growing season appears to influence where the species grows. Alder can tolerate poor drainage conditions and some flooding during the growing season; consequently, it prevails on soils where drainage is restricted-along stream bottoms or in swamps or marshes. It is not commonly found on droughty soils, however; and in areas of low precipitation, it seldom grows on steep south or southwest-facing slopes. In Idaho and California, stands are usually limited to borders of streams or lakes.

Red alder develops best on elevations below 450 in (1,480 ft) in northern Oregon, Washington, and British Columbia. In Alaska, red alder generally occurs close to sea level. Farther south, scattered trees are found as high as 1100 in (3,610 ft), but most stands are at elevations below 750 in (2,460 ft).

Special Uses
Red alder wood is diffuse-porous, moderately dense, and uniformly textured. It is used in the production of solid wood products, such as furniture, cabinets, case goods, pallets, and novelties; composite products, including plywood and flakeboard; and fiberbased products, such as tissues and writing paper.

Alder is a common fuelwood and is burned both in home fireplaces and stoves, and in mills that use residues to produce heat for drying and other processes. Because of its rapid juvenile growth and ability to coppice, red alder has been evaluated for use in biomass farms for energy conversion; some experimental plantings have been made to evaluate yields under intensive management.

The ability of red alder to fix atmospheric nitrogen can result in increases in both nitrogen content and its availability in the soil. Nitrogen fixed irr the nodules is added to the soil in four ways: direct excretion from living roots or nodules, decomposition of dead roots or nodules, leaching from foliage, and decomposition of litter rich in nitrogen. Fixation rates vary diurnally and seasonally and with site and stand age. Maximum annual fixation rates of 320 kg/ha (290 lb/acre) (36, based on accretion) in pure stands and 130 kg/ha (120 lb/acre)in mixed stands have been reported.

Red alder also increases the organic matter content in the soil. Concomitant with increases in soil organic matter, decreases in soil bulk density and pH have been reported.

Red alder has been proposed for use alone and in both crop rotation and mixture with other species. Because of its ability to add nitrogen and organic matter to a site and its rapid juvenile growth on a variety of sites, the species has been experimentally planted as follows: (a) to serve as a nitrogen source for other species (particularly Douglas-fir and black cottonwood); (b) on coal mine spoils, landslides, and other eroded or low fertility areas; (c) for streambank or roadside protection; (d) in areas of poor drainage; (e) as a firebreak or windbreak; and M for wildlife areas.

An additional experimental use of red alder in a crop rotation system is to plant it in areas containing coniferous root pathogens, such as Phellinus weiri, which can survive for many years in organic materials in the soil. The only known control is to replace the disease-susceptible species with a nonsusceptible species for 40 to 50 years. Red alder is a good candidate for such an interim species.

Other experimental uses of alder include addition of foliage, twigs, and sawdust to grain or alfalfa for cattle feed and addition of sawdust to nursery soils to increase organic matter.

Red alder grows exclusively west of the Cascades between Alaska and California, except for a few isolated stands in Idaho. You can find Red alder growing in Hawaii, where it was introduced for cultivation. Before settlers came to our Northwest region, alder was restricted to growing alongside streams and wet areas. However, with our expanding population and the logging industry’s clear-cutting practices, alder is now quite abundant throughout the region.

Alder is our most abundant hardwood, used for making fine furniture and cabinets around the world. Alder is still considered the best wood for smoking salmon. Salish and coastal tribes once ate the inner bark of alder, scraping it off in spring and mixing it with oil or drying it in cakes for winter use. Clothes, utensils, dyes and medicines also came from the alder.

Population Differences
Population differences in height growth, diameter growth, stem form, bark thickness, and resistance to frost or insect attack have been demonstrated in a provenance trial in coastal Oregon involving 10 sources from the range of red alder . High growth rates were positively correlated with good form but negatively correlated with resistance to spring frosts. Differences among provenances in bole volume or aboveground biomass were greater than differences in height or diameter alone. Specific gravity did not differ significantly among provenances, nor was it correlated with growth rate.

The fastest growing trees in the provenance trial were from northwestern Washington, but trees from British Columbia, southwestern Washington, and Oregon also grew well. The slowest growing trees were from Alaska and Idaho. Thus, it appears reproductive material of red alder can be moved to mild sites over fairly long distances along the Pacific coast.

Differences in form and in characteristics of branch, bark, and wood among eight stands in western Washington have also been assessed. Variability among trees in a stand was high; only bark thickness, a branch diameter index, branch angle, and a crown-width index differed significantly among stands.

A cut-leaf variety (Alnus rubra var. pinnatisecta) is found in a few isolated areas in British Columbia, Washington, and Oregon. The cut-leaf characteristic is caused by a single recessive gene; thus, the cut-leaf variety can be used as a marker in genetic breeding studies.

Families varied in their height-growth response to water-table depth in a 24-family progeny trial in western Washington. Use of genotypes tolerant of waterlogging may enhance growth of red alder on wet sites.

Phenotypic variation between trees is high. Studies are underway to assess genotypic variation and the heritability of various traits. An individual tree approach for selection has been recommended for tree improvement programs. Because red alder has extensive populations of even-aged stands and because of its reproductive and growth characteristics, the species has the potential for rapid genetic gains.