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Thinleaf (Mountain) Alder   arrow

Alnus tenuifolia (al’-nus ten-ewe-i-fo’-lee-a)
Family: Betulaceae, Birch

Key Steps


Thinleaf Mountain AlderLeaf: Coarsely, double-toothed, broad, round tip, wedged base, 6-8 pairs of veins. Tufts of hair in veins axils beneath. Hairy stipules, 1/2 inch long. Orange-colored central vein beneath. Stout, grooved petiole, 1 inch long.

Bud: Stalked, 1/3″ long, bright red, a little hairy. Two or more scales, barely meeting. True terminal bud absent.

Leaf Scar: Half round, raised

Stem: Slender, not peeling. Tight bark. Young: rusty, hairy. No wintergreen or spicy taste or odor.

Bark: Smooth, becoming scaly with age. Light brown to gray.

Pith: Triangular in cross section.

Flower: Female: egg-shaped strobile before leaves. Male: 2-4 inch long catkin, 3-5 clustered together.

Fruit: Persistent woody strobile, looks like a miniature cone. Less than 1 inch long.

Habit: Birch-like, slender. May be multi-stemmed. To 15 feet tall, upright, clump forming.

Culture: High water needed; use in moist sites. Alders fix nitrogen in the soil, similar to legumes.