Alnus incana (L.) Moench ssp. rugosa (Du Roi) R.T. Clausen
Alnus incana (L.) Moench var. americana Regel
Alnus rugosa (Du Roi) Spreng.
Alnus rugosa (Du Roi) Spreng. var. americana (Regel) Fernald
Speckled alder, tag alder, hoary alder, gray alder
Alders are small to medium in size, often with multiple trunks and branches. Speckled alders grow to 12-36' (3.7-10 m), rarely reaching 60' (18 m), usually less than 20' (6.1 m) tall. These fast-growing trees are often found beside wet areas. The subspecies name, rugosa, means “wrinkled,” and refers to the network of sunken veins on the bottom surface of each leaf. Alder roots, like many legumes, are capable of converting atmospheric nitrogen into usable nutrients, allowing them to grow in relatively infertile soil. These densely branched shrubs, with their penchant for growing in muddy soil and rapid spread by creating clonal colonies, form nearly impassable thickets.
Identification: These alders may be multiply branched large shrubs or small trees.”Speckled” refers to the presence of many lenticels—white, or light gray or orange oval patches, wider than they are flat, on the trunk. Leaves are dark green, alternate, roughly oval, 2-4" (5-10 cm) long, and doubly serrated. Male flowers are catkins 1½-3½" (3.8-8.9 cm) long. Female flowers are cylindrical catkins attached directly to the branch, ⅛" (4.8 mm) long. The fruits are egg-shaped cones about ⅝" (1.6 cm) × ¼" (7.9 mm), green at first, becoming dark brown and often persisting through the winter.
Alnus incana ssp. rugosa on Earl J.S. Rook's Flora, Fauna, Earth, and Sky ... The Natural History of the Northwoods
Alnus incana ssp. rugosa at the Virginia Tech Department of Forest Resources and Environmental Conservation
Alnus incana ssp. rugosa at the Lady Bird Johnson Wildflower Center
Alnus incana ssp. rugosa description by Thomas H. Kent, last updated 25 May 2020.