Description & Range

PNW Native; Ranges from S. Alaska through N. California
Red alder grows in a single thin erect trunk reaching heights of up to 25 m / 100 ft with bark most commonly white-grey from lichen growth, green-grey in urban environments. (DM) Leaves are deciduous, alternate, with serrated margins, green and smooth on apical surface and light green with fine hair on basal surface, 2 – 8 in. /5 – 15 cm long, and fall during winter while they are still green. Male and female flowers are separate, appearing on the same tree before leaves. Male catkins are 5 – 12 cm / 2.5 – 6 in. Female catkins at first appear compact, with a maximum length of 2 cm / 1 in. Once fertilized, female catkins develop into woody cones with seeds inside during late fall and remain on the tree until the next spring. (PM)

Ecology

Red alder grows rapidly, often reaching heights of 35 ft/10 m within a decade. Due to their growth rate, only young saplings are available as browse to animals such sheep, goats, deer, elk, and cattle. Beavers use the branches and stems to create their dams. Birds such as goldfinches, redpolls, and siskins, and rodents like deer mice, consume the seeds. (U) Red alder has a relationship with the fungus-like, hyphae forming bacteria known as symbiotic nitrogen-fixing bacteria in its roots, which combined with its rapid growth rates, causes alder to be the one of the first stages of ecological succession in the development of local forests. (M)
Red alder’s roots get invaded by Frankia which is an actinomycete, a fungus-like, hyphae forming bacteria that fixes atmospheric nitrogen into a form usable by plants. These bacterial colonies appear as nodules on the roots. Nitrogen abundance in soil in the Pacific Northwest tends to be the primary limiting nutrient for plant growth, and red alder stands can contribute as much as 320 kg/ha to the soil. (PM) Another notable symbiote of red alder is the lichen that grows on the tree trunk and gives the tree its notable white-grey and textured appearance. This lichen is not present in areas with high amounts of air pollution, so in cities the tree bark will appear green-grey and smooth. (DM) 
The importance of red alder to forest formation in the Pacific Northwest cannot be overstated. Due to their nitrogen fixing capabilities, ready propagation from clones, formation of nutrient-rich soil from dropped leaves full of nitrogen, and creation of an overstorey and understorey, red alders are the first plant species to colonize barren ecosystems unaccustomed to plant life, clear cuts, burns, and other disturbed ecosystems. Their short lifespans allow conifers like Douglas-fir to replace their place in the overstorey and are directly responsible for creating the nutrient-rich old growth temperate forests of the Pacific Northwest, and after deglaciation from the last ice age, alder forests dominated the region for thousands of years, enriching the soil and facilitating soil ecosystems that later gave way to the iconic coniferous forests of the region. Red alder also has the potential to benefit from increased atmospheric CO2 caused by climate change. (DM) 
In an undisturbed ecosystem, red alder is typically found along streamsides and swamps at low to middle elevations. However, with the colonization of the Pacific Northwest, white settlers clearing swathes of land previously dominated by old-growth forests found red alders quickly reclaiming these sites, especially those selected for timber farming. At the time, their soil-enriching benefits were not known and they were treated as a pest, but now many tree farms interplant red alder with Douglas-fir for its nitrogenous benefits. (DM)

Cultural and Historical Significance

Red alder naturally contains salicin, which is similar to acetylsalicylic acid, found in willow bark and the active ingredient in aspirin (acetaminophen). This explains red alder’s use in many traditional Native American medicinal preparations. Wood was also used for making utensils. Red alder smoked salmon is a regional delicacy in the Pacific Northwest. People of the region also made red-orange-brown dye from the bark, (U) which was the most commonly used dye along the Northwest coast tribes. This dye was used to make fishing nets invisible to salmon, since they have a harder time seeing the red color range. Soft inner bark and cambium were eaten by the Saanich in the late Pleistocene and early Holocene. Bowls carved from red alder have been found at the significant Ozette site. Paddles, canoe bailers, firedrills, masks, bowls, and trays, and firewood were all harvested from red alder. Saplings and young limbs were used in fish weir construction. An infusion of red alder bark was used as a tuberculosis treatment, bark decoctions were made, and both were used as rinses for various skin ailments and infections. In Haida and Nlaka’pamux mythologies, red alder is personified as the supernatural wife of Coyote. To honor her, it is Haida custom to hug a red alder tree before felling it.  (Turner) 
In the Pacific Northwest, red alder is the wood used to give smoked salmon its iconic flavor, and alder-smoked salmon is prized as a local delicacy. (PM)

Economics

Red alder is the most important commercial hardwood in the PNW. The texture and grain is consistent and even, it holds polish and varnish well, it is easy to work, and it rarely splits. Red alder is also much more cost-efficient than other hardwoods used due to its shorter growth cycle and easy workability. Smaller logs (less than 8 in/20 cm in diameter) are used for this purpose. Logs larger than this are fit for a sawmill. Red alder is manufactured into paper, brush handles, trays, shoe soles, boxes, plywood, wood veneer, trim, cabinetry, pallets, paper roll plugs, and furniture. (U) 

Red alder interplanting also boosts productivity of Douglas-fir farms, and red alder is naturally toxic to laminated root rot. This, combined with its role in ecological succession in Pacific Northwest forests, causes red alder to be used widely in ecological restoration. (DM)