Virginia Tech Dendrology

red alder Betulaceae Alnus rubra Bong. symbol: ALRU2
Leaf: Alternate, simple, deciduous, ovate, 3 to 6 inches long, prominently penniveined leaf with doubly serrate margins that are tightly rolled under at the edges (revolute); petiole 1 inch long and grooved; green to yellow green above and paler green below.
Flower: Species is monoecious but flowers are borne in unisexual aments (catkins); preformed males are slender, pendent, and hang in clusters of 2 to 5; female catkins are short and thick, borne at the ends of branchlets.
Fruit: A small semi-woody cone about 1/2 to 1 inch long, persists through the winter, brown, seeds are tiny winged nutlets, shed in the fall.
Twig: Young twigs are distinctly triangular in cross-section; olive to reddish brown; prominent lenticels; clearly stalked buds.
Bark: Ashy gray to grayish brown, generally smooth but breaking into flat, irregular plates near the base, increasingly covered with white lichens as it ages; inner bark is tan but turns red when exposed to air.
Form: A medium sized tree reaching 120 feet tall and 1 to 3 feet in diameter. Typically has a moderately straight bole with an open, broadly pyramidal or dome-shaped crown. Lower trunk is usually free of branches due to intolerance to shade.
Looks like: white alder - Sitka alder - thinleaf alder - Arizona alder

Additional Range Information: Alnus rubra is native to North America. Range may be expanded by planting. Download the full-size PDF map.
More Information: Wood - Landowner Factsheet
External Links: USDAFS Silvics of North America - USDAFS FEIS Silvics - USDA Plants Database - USDAFS Forest Products Lab
All material 2025 Virginia Tech Dept. of Forest Resources and Environmental Conservation; Photos and text by: John Seiler, Edward Jensen, Alex Niemiera, and John Peterson; Silvics reprinted from Ag Handbook 654; range map source information