Alder, Thinleaf - Alnus incana spp. tenuifolia

A large shrub up to 12 m (40 feet) tall; bark is thin, smooth, dirty green-gray and tends to flake when older; stems are somewhat threesided, sometimes with short rusty hairs, and pith turns rusty color when freshly cut; roots are nitrogen fixing; leaves are alternate, deciduous, dull green on both sides and yellow-green on central vein, not sticky, with double dentate margins; flowers catkins; fruit winged nutlet in semi-woody small cone. Habitat is moist montane woods and streambanks at mid to lower elevations on coarse textured soils. Collect seed in September through November; irregular crops every 1 to 4 years; fresh seed germinates without cold stratification; fall collected and sown seed germinates readily; air-dried seed can be stored in sealed containers at 1 to 3°C (34 to 37°F) for up to ten years; dried/stored seed requires a 180 day cold stratification at 5°C (41°F) before germination will occur. Transplant seedlings at one to two years old. Little information is available on asexual propagation but the tendency for this species to form adventitious roots when submerged in water suggests it is possible.

Greenhouse asexual propagation - June and July softwood cuttings treated with 8,000 ppm IBA is generally recommended for Alnus species.

Field propagation by dormant unrooted hardwood cuttings is very difficult. It has been reported that dormant unrooted hardwood cuttings will root if they are placed in soil that has been collected from under mature alder. The theory is that the microbes will cause the cuttings to root. In addition, small seedlings can be collected from under mature trees and potted in containers for eventual reestablishment in riparian zones.

< Back to Species Descriptions and Propagation Techniques

Last Modified: 07/05/2007