European black alder
FULL SCIENTIFIC NAME
Alnus glutinosa (L.) Gaertn.
FAMILY NAME COMMON
FAMILY SCIENTIFIC NAME
Branch with fruits
Fruit with leaves
Branch with fruit
Close-up of fruit
Synonyms: Alnus alnus (L.) Britton
Alnus vulgaris Hill
Alnus glutinosa is a rapidly growing tree that can reach 20 m (65 ft.) in height. The tree often has a multi-stemmed trunk. The bark is smooth and dark brown, but can show some shallow fissures with age. The leathery leaves are obovate to nearly orbicular in shape and are 3-9 cm (1-3.5 in.) long and 3-8 cm (1-3 in.) wide. The leaf bases are rounded to broadly cuneate and the margins of the leaves are coarsely or irregularly doubly serrate. The teeth can be acute to obtuse or nearly rounded. The upper leaf surface is glabrous, while the veins of the leaf on the lower surface are pubescent. The young leaves are coated in resin. The leaves of this plant persist late into the fall. Alnus glutinosa is monoecious. The catkins are glutinous, with the staminate catkins being in one or more clusters of 2-5, and are 4-13 cm (1.5-5 in.) long. The pistilate catkins are much smaller and they are also in one or more clusters of 2-5. The flowers appear on the tree before the new growth in the early spring. The hard fruits are ovoid to nearly globose and measure 1.2-2.5 cm (0.5-1 in.) long and 1-1.5 cm (0.5 in.) wide. The seeds are obovate and have short and narrow wings. Page References Bailey 327, Crow & Hellquist 72, Fernald 539, Flora of North America 511, Gleason & Cronquist 91, Holmgren 84, Magee & Ahles 402. See reference section below for full citations.
Alnus incana (L.) Moench (speckled alder)
A. serrulata (Ait.) Willd. (hazel alder)
A. viridis (Vill.) Lam. & DC. (green alder) Alnus glutinosa has similar leaves, flowers and fruits to the native bush alder species of the U.S. However, A. glutinosa is a tree and can grow much bigger than the natives.
Alnus glutinosa reproduces by mechanically dispersed seeds. Dispersal by water may play a major role in its spread along waterways. Wind plays a minor role in its dispersal, most notably when the seeds are able to blow over the top of crusted snow.
Alnus glutinosa is native to Europe, northern Africa and western Asia. In the United States it is found from Vermont to Minnesota and south from Tennessee to Nebraska. The USDA Plants Database reports that it is present in Vermont, Massachusetts and Connecticut, but it has also been collected in Rhode Island. It is locally naturalized within its New England distribution. The degree of its naturalization, as opposed to its horticultural presence, has not been fully established.
HISTORY OF INTRODUCTION IN NEW ENGLAND
Alnus glutinosa has been in cultivation in the northeast since colonial times. Early records have it escaping cultivation on Long Island as early as the 1870's (J. of the Torrey Botanical Club 1876, Vol. 6: 115, 259). A 1900 record (Rhodora, Vol. 2: 157) has it "well established" in West Medford Massachusetts, though there was "no record of introduction." Fernald (1950) reported that it was "locally naturalized" from Newfoundland to Illinois and south from Delaware to Pennsylvania.
HABITATS IN NEW ENGLANDEarly Successional Forest, Edge, Floodplain Forest, Forest Wetland, Roadside, Shrub Wetland, Yard or Garden
Alnus glutinosa grows best in low lying areas with moist, acidic soils. It is commonly found along stream banks and other waterways.
This plant's tendency to be disperse by water, and its ability to form monospecific stands, makes it a threat to native wetland species. Alnus glutinosa can fix nitrogen, giving it the ability to become established on very poor soils.
Documentation required: A specific photograph of the habit with flowers or a mounted snippet with flowers.
Best time for documentation: All seasons.
Integrated Taxonomic Information System
Taxonomic information about the species
The PLANTS Database
General information and map
Flora of North America
Description and distribution map
USDA Forest Service-Silvics of North America
Extensive description and ecology of this species
Virginia Tech Dendrology
Description and photographs
Bailey, L. H. 1949. Manual of Cultivated Plants. Macmillan, New York. Crow, G.E. and C.B. Hellquist. 2000. Aquatic and Wetland Plants of Northeastern North America. Vol #. University of Wisconsin Press, Madison. Fernald, M. L. 1950. Gray's Manual of Botany, 8th edition. American Book Company, Boston Flora of North America Association ed. 2000. Flora of North America vol. 3. Oxford University Press, Oxford, New York. Gleason, H. A. 1952. The New Britton and Brown Illustrated Flora of the Northeastern United States and Adjacent Canada. Macmillan Publishing Co., Inc. New York Gleason, H.A. and A.C. Cronquist. 1991. Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed. New York Botanical Garden, Bronx, New York. Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. New York Botanical Garden, Bronx, New York. Magee, D.W and H.E. Ahles. 1999. Flora of the Northeast. University of Massachusetts Press, Amherst. USDA, NRCS. 2001. The PLANTS Database, Version 3.1. (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.