Alder (Alnus spp.) is represented by 20 to 30 species, with 15 species in North and Tropical America and 15 species in Eurasia. All species look alike microscopically. The word alnus is the classical Latin name of alder.
Red alder (Alnus rubra) is the only commercial species in North America. Red alder is the most common hardwood in the Pacific Northwest and the largest of the American alders. It is a fast-growing, pioneer species and has nitrogen-fixing nodules on its roots. The wood is diffuse porous, moderately light, and soft.
Other Common Names: Amerikaanse rode els, aliso Americano, aune d’Oregon, ontano dell’Oregon , Oregon-al, Oregon alder, Oregon erle, Pacific Coast alder, western alder.
Other American Species:
Alnus maritima seaside alder
Alnus oblongifolia Arizona alder, lanceleaf alder, Mexican alder, New Mexican alder, oblong-leaved alder
Alnus rhombifolia* Oregon-al, sierra alder, white alder
Alnus rugosa gray alder, hazel alder, hoary alder, smooth alder, speckled alder, tag alder
Alnus serrulata black alder, common alder, hazel alder, smooth alder, tag alder
Alnus sinuata green alder, mountain alder, northern alder, sitka alder, wavyleaf alder
Alnus tenuifolia al amerikansk, aliso Americano, aune du canada, California alder, mountain alder, ontano American, river alder, rhombic-leaved alder, thinleaf alder, western alder, white alder
* commercial species
Distribution: North America: Pacific coast region from southeastern Alaska to western British Columbia and south through western Washington and western Oregon to southern California. The range of red alder extends from southern California (latitude 34oN) to southeastern Alaska (60oN). Red alder is not commonly found east of the Cascade or Sierra Nevada Ranges, although there are several isolated populations in northern Idaho. The species develops best at low elevations of less than 1,500 ft (457 m) in northern Oregon, Washington, and British Columbia. In the central part of its range, scattered trees occur as high as 3,300 ft (1,006 m), but most stands are below 2,500 ft (762 m).
The Tree: On good sites, red alder can attain heights of 100 to 130 ft (30 to 40 m) and diameters of 22 to 30 inches (56 to 76 cm). In closed stands, the trees typically have clear, slightly tapered boles and narrow, domelike crowns. The light gray bark is thin and smooth. Red alder forms extensive, fibrous root systems. The roots have numerous nitrogen-fixing nodules, which are a symbiotic association between the tree and beneficial bacteria belonging to the genus Frankia.
General Wood Characteristics: Red alder wood is almost white when freshly cut but quickly changes to a light tan or light brown with a yellow or reddish tinge when exposed to the air. Heartwood is formed only in trees of advanced age, and there is no visible boundary between heartwood and sapwood.
Weighta
Weight
Moisture Specific lb/ft3 kg/m3
content gravity
Green 0.37 46 737
12% 0.41 28 449
Ovendry 0.43b NA NA
aReferences: specific gravity (98), weight
(59).
bReference (59).
Mechanical propertiesa
Property Green Dry
MOE 1.17 106 lbf 8.067 GPa 1.38 106 9.515 GPA
/in2 lbf/in2
MOR 6.50 103 44.818 MPa 9.80 103 67.571 MPa
lbf/in2 lbf/in2
C| | 2.96 103 20.409 MPa 5.82 103 40.129 MPa
lbf/in2 lbf/in2
C 0.25 103 1.724 MPa 0.44 103 3.034 MPa
lbf/in2 lbf/in2
WML 8.0 55.160 kJ/m3 8.4 in-lbf/in3 57.918
in-lbf/in3 kJ/m3
Hardness 440 lbf 1,957.12 N 590 lbf 2,624.32 N
Shear| | 0.77 103 5.309 MPa 1.08 103 7.446 MPa
lbf/in2 lbf/in2
aReference (98).
Drying and shrinkagea
Percentage of shrinkage
(green to final moisture
content)
Type of 0% MC 6% MC 20% MC
shrinkage
Tangential 7.3 5.8 2.4
Radial 4.4 3.5 1.5
Volumetric 12.6 10.1 4.2
aReferences: 0% MC (98), 6% and 20% MC
(90).
Kiln drying schedulea
4/4, 5/4, 8/4 10/4 12/4 16/4
Condition 6/4 stock stock stock stock
stock
Standard T10-D4 T8-D3 T6-C3 T6-D3 NA
Darker T11-D3 NA NA NA NA
Lighter T5-D5 NA NA NA NA
aReferences (6, 86).
Working Properties: Red alder is excellent for turning and polishing and takes glue, paint and stain well.
Durability: Rated as slightly or nonresistant to heartwood decay.
Preservation: Logs should be processed quickly, particularly during warm weather, as decay proceeds rapidly. If processing must be delayed, the logs should be stored in water. Green lumber should be carefully stacked for air-drying or promptly kiln-dried to prevent damage from microbial stain.
Uses: Nonstructural lumber, factory appearance-grade lumber, chips for pulp and paper, furniture, cabinets, pallets, core stock for plywood, interior finishing, fuelwood, charcoal, chips for smoke curing.
Toxicity: Can cause dermatitis (64).
Additional Reading: 7, 29, 32, 38, 39, 55, 62, 68, 55, 66, 68, 74, 79. 28, 29, 42, 43, 44, 48, 50, 55, 56, 68, 72, 73, 74, 79, 92, 97, 102. 74, 75, 77, 99, 106.