Speckled Alder – Alnus incana
Speckled Alder is a tall, deciduous, thicket-forming shrub or small tree, to 20′ tall. Its leaves are dark green above, light yellow-green and pubescent underneath, ovate to elliptic in shape with doubly toothed and shallowly lobed edges.
Grows best in full sun, moist, nutrient-rich soil. Good choice for disturbed site rehabilitation and providing streambank stability and erosion control.
All of the alders associate symbiotically with species of the actinomycete Frankia, leading to the formation of nodules on the roots of the plants and the fixation of atmospheric nitrogen.
Speckled alder provides winter cover for snowshoe hare. Moose, muskrats, beavers, cottontail rabbits, and snow-shoe hares feed on the twigs and foliage. Low preference white-tailed deer browse, avoided by moose in the Lake Superior region.
Most common in the region surrounding the Great Lakes and the St. Lawrence, including east-central Canada, the Maritimes, and the Northeast and Lake States. Grows primarily in moist lowlands, frequently bordering streams and lakes, common in swamps and the older zones of bogs.
Speckled alder grows throughout Wisconsin in wet soils and full sun to very light shade. It is the namesake of a type of wetland known as “alder thicket”.
1. Speckled alder, Morton Arboretum acc. 204-97-1 photos by Bruce Marlin
2. United States Department of Agriculture NRCS Plant Fact Sheet 565
3. University of Wisconsin at Green Bay, Trees of Wisconsin, “speckled alder; tag alder”