Broadleaf, deciduous, large spreading shrub, 3-13 ft (1-4 m) tall. Twigs smooth, dark brownish red, with many light lenticels (appear as dots). Leaves alternate, simple, ovate or broadly elliptic, about 4-9 cm long and 2.5-5 cm wide, thick, apex short-pointed, base rounded or broadly wedge-shaped, margin sharply and finely toothed, sometimes undulated, shiny yellow green upper surface, pale green and with tuft of whitish hairs in vein angles. Male flower catkins 2-7.5 cm long and female clusters only 6-10 mm long. Fruit, cone-like, 10-15 mm long , yellow then brown, with a slender stalk.
Sun to shade, best in moist soil
Hardy to USDA Zone 1 This species is widely distributed throughout interior, central, and northern Alaska across the Yukon Territory and interior Canada to Labrador, Newfoundland, and Greenland. It extends south through New England and the Great Lakes States, and into the Pacific Northwest.
- Recent studies have shown that American Green Alder is part of a circumpolar alder group (Alnus viridis) distributed across America, Europe, and Asia. This species has been separated into three subspecies, including (1) A. viridis supsp. crispa - American Green Alder, and (2) A. viridis subsp. sinuata - Sitka Alder.
- Note: The common name, Mountain Alder, is applied to Alnus viridis supsp. crispa and Alnus incana subsp. tenuilolia
- viridis: green, crispa: curled