Northern Prairie Wildlife Research Center
Western Wetland Flora
Field Office Guide to Plant Species
Alnus tenuifolia Nutt.
- Family: Birch (Betulaceae)
- Flowering: April-June
- Field Marks: This usually shrubby alder is distinguished by its doubly toothed and
sometimes lobed leaves that are rounded or heart-shaped at the base.
- Habitat: Moist woods, along streams, mountain meadows.
- Habit: Shrub or rarely a small tree up to 20 feet tall.
- Twigs: Smooth, but with conspicuous white lenticels.
- Bark: Smooth, gray or reddish brown.
- Leaves: Alternate, simple, ovate to oblong, up to 4 inches long, pointed or rounded at the tip, rounded or heart-shaped at the base, doubly toothed and sometimes shallowly lobed,
paler on the lower surface, with hairy veins.
- Flowers: Male and female flowers borne separately but on the same plant; male spikes
slender, drooping, up to 3 inches long; female spikes upright, up to 1/2 inch long; flowers
open before the leaves unfold.
- Sepals: 4 in the male flowers, 0 in the female.
- Petals: 0.
- Stamens: 4, attached to the base of the sepals.
- Pistils: Ovary apparently superior.
- Fruits: Nutlets up to 1/8 inch wide, with a narrow, membranaceous wing, borne in a
- Notes: Thin-leaf alder is sometimes known as Alnus incana ssp. tenuifolia.
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