red alder Betulaceae Alnus rubra Bong. Listen to the Latin symbol: ALRU2 Other Fact Sheets
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
leaf flower fruit twig bark form map
Additional Range Information:
Alnus rubra is native to North America.
Range may be expanded by planting.
See states reporting red alder.
More: Wood
External Links:
USDAFS Silvics of North America
USDAFS Additional Silvics
Landowner Factsheet
USDA Plants Database
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Dept. of Forest Resources
and Environmental Conservation,
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Photos and text by: John Seiler,
Edward Jensen, Alex Niemiera,
and John Peterson
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