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Northeast Wetland Flora

Field Office Guide to Plant Species

European Alder
Alnus glutinosa (L.) Gaertn.

JPG -- Species Photo JPG -- Distribution Map

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.

Previous Species -- Green Alder (Alnus crispa)
Return to Species List -- Group 5
Next Species -- Seaside Alder (Alnus maritima)

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Page Last Modified: Thursday, 03-Aug-2006 11:39:25 EDT
Menlo Park, CA [caww55]