rubra – red (Latin), referring to inner bark that is orange-red so trunk wounds turn red

Native range: Coastal N. America, Idaho

Leaves:

• alternate
• simple
• broadly elliptic (1.5–3” wide)
• acute base
• deep and doubly serrate
• revolute at base of leaf
• dull green above, rusty colored below
• revolute (rolled under) margin

Flowers:

• monoecious
• male – long pendulous catkins develop before the leaves on growth of the previous season
• female – short upright catkins

Fruit:

• wooden, cone-like
• small (1/2–1” long)
• persist on tree over the winter
• each cone contains up to 100 small nutlets that are wind dispersed

Other characteristics:

• deciduous tree
• thin grayish white smooth bark
• lenticels in bark
• root sprouts, found in groves
• often with white patches of lichen on bark

Relevant info:

• lives up to 100 yrs, reaching 80–100 ft.
• largest American alder
• generally short-lived, early successional species
• Native Americans:
  • used inner bark to dye fish nets, making it harder for fish to avoid them
  • used for medicinal purposes: contains salicin, which is closely related to acetylsalicylic acid (AKA aspirin)
  • wood used for utensils
  • coals used to smoke salmon
• important commercial tree
  • wood used to make inexpensive furniture, small wooden items, and paper pulp

Ecology & Adaptations:

• native chiefly west of the Cascades crest in Washington
• Alaska south to California, disjunct to the east in northern Idaho
• found at low elevations in moist woods, streambanks, floodplains, [land]slide tracks, recently cleared land (often in pure stands)
• sexual reproduction:
  • drooping staminate (male) catkins are up to 12 cm long and clustered near the end of a twig
  • pistillate catkins are erect, 1.5-2 cm long, turning woody and conelike at maturity
• pollination by wind
• seed dispersal:
  • wind carries lightweight winged seeds
  • seed production is normally so prolific that dense stands quickly develop on exposed soils of clearcuts and burned areas
• adapted to wetlands:
  • lenticels (pores) in bark facilitate transfer of oxygen to roots when soils are saturated
  • shallow root system facilitates access to oxygen
• herbivore defense:
  • leaves contain tannins that reduce digestibility of tissue by binding with proteins
  • leaves, wood, and bark contain Oregonin, a glycoside, that reduces palatability and digestibility
• adapted to low-nutrient conditions – association with N-fixing bacteria in root nodules enables species to survive in disturbed and low-nutrient environments and enhance the protein content of the leaves
• fire resistance:
  • thin bark is sufficiently fire resistant to protect trees from light surface fires
  • foliage and leaf litter do not carry fires well
  • stands often lack flammable understory debris and are often on moist sites, which burn infrequently
  • revegetates burned areas via seed from off-site plants
• succession & disturbance:
  • early successional species
  • ability to establish is due in part to association with nitrogen-fixing bacteria
  • red alder communities were primarily restricted to streams and wet areas before European contact
  • since then, disturbances such as logging have provided an abundance of open sites with bare mineral soil, which favor red alder colonization.
• wildlife:
  • as defense compounds decrease in concentration in autumn, leaves provide a significant source of protein to black-tailed deer and Roosevelt elk, especially as other sources of protein diminish
  • beavers eat the bark, and build dams and lodges with the stems
  • seeds eaten by birds (redpolls, siskins, goldfinches) and deer mice