Northern Prairie Wildlife Research Center
Northeast Wetland Flora
Field Office Guide to Plant Species
Alnus glutinosa (L.) Gaertn.
- Family: Birch (Betulaceae)
- Flowering: March-May
- Field Marks: This alder is a tree with 1-5 female spikes in a cluster, the flowers blooming in
the spring. The young twigs and fruiting spikes are very sticky. It differs from the seaside
alder in having straight rather than curved veins.
- Habitat: A variety of habitats, often along roadsides.
- Habit: Tree up to 100 feet tall (at least in its native Europe), with a broadly rounded crown, the trunk straight, eventually with dark brown bark.
- Twigs: Without hairs but sticky, particularly when young; buds short-stalked.
- Leaves: Alternate, simple, dark green, ovate to nearly spherical, rounded at the tip, rounded or somewhat tapering to the base, finely or coarsely toothed, without hairs, up to 6 inches long, sometimes nearly as broad, with a stalk up to 1 inch long.
- Flowers: Male and female flowers borne separately but on the same plant, the male flowers 3 in a cluster and subtended by 4-5 bractlets, all in a slender spike up to 3 inches long, the female in 1-5 ovoid spikes in a cluster, each spike up to 1 inch long and sticky, borne on long stalks.
- Sepals: 3-5, minute, green, united to each other, or absent.
- Petals: 0.
- Stamens: 3-5.
- Pistils: Ovary inferior.
- Fruits: Many nutlets aggregated into a "cone," with each nutlet subtended by a woody bract, the nutlets nearly spherical, unwinged, 1/10-1/8 inch in diameter.
- Notes: This species, a native of Europe, is sometimes called black alder.
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