Alnus rubra
(Red Alder)
[Bong.]

Subclass: Hammamelidae
Order: Fagales
Family: Betulaceae
Family Description: Birch

Key Characteristics:
Trees up to 25 meters tall; new twigs generally glabrous
leaves
flowers
fruit
  • blades sinuate, broadly elliptic to ovate-elliptic, lobed to dentate;
  • 5-15 cm long; margins slightly revolute;
  • acute at both base and apex;
  • generally paler beneath than above, usually somewhat rusty-gray hairy beneath and strongly glandular in dots
  • flowers are unisexual in unisexual catkins which develop before leaves of current year
  • Both pollen and pistillate flowers are subtended by a bract which subtends 2 smaller bracteoles
  • male catkins soft & pendant, 5-12 cm long; each flower has a 4-parted perianth encircling 3-4 stamens
  • female catkins are hard; each persistent scale subtends 2-3 bracteoles which subtend 2 flowers which have no perianth; 1.5-2 cm long and 1 cm in diameter borne on stout peduncles less than one cm long.
  • has a membranous wing 1/5-1/2 as wide as the nutlet

General Description:
This rapidly growing tree can reach 25 feet tall with up to an 8 inch diameter trunk. The bark is thin, gray, and smooth. The wood tends to turn a deep red. The alternately arranged leaves are elliptic, 5-15 cm long with acute bases and apexes, and revolute, irregularly serrate margins. The upper glabrous surface is deep green while the lower surface is rusty gray, hairy and glandular-dotted. The catkins flower while the leaves are developing. They are on previous season's growth. Male catkins are 5-12 cm long and drooping. The female catkins are woody, about 1 ½ to 2 cm long, and bear winged fruits on their upper surface. They grow in moist woods, often along streams in Northern Idaho. The wood is used mostly for burning, but is also made into attractive hardwood furniture. Also known as Oregon Alder.

Distribution:
Alaska southward , west of the Cascades to California and in Northern Idaho.

Habitat:
Grows in moist woods, mostly below 1000 feet elevation.

Other:
Sometimes considered a weedy species useful only for firewood, but recently has been utilized for furniture building. The cones have also been gold plated and sold as “pine cones.”

Important State References:
No information available at this time
Photos and Information written by Dr. Karl E. Holte,© 2002