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Fact Sheet No. 241, UMaine Extension No.2194

Prepared by David E. Yarborough and Timothy M. Hess, The University of Maine Orono, ME 04469. Replaces March 1997 by Tom Degomez, David Yarborough and Christopher Campbell.  Revised April 2002.

Grey Birch, Betula populifolia
Slender tree with smooth white bark. Leaves dark green, triangular with a long tapering tip, 1.5″-2.5″ long and 1″- 2″ wide. Buds have sharp points that point away from the twig. Unisexual flowers, male catkins are preformed in the summer and over winter, 1.5″ to 2.5″ long when mature in the spring; female catkins 0.5″ long and slender. The fruit’s thin wings broader than the nutlet. Prefers dry, upland soils.

Gray birch
Figure 1: Grey Birch
Grey birch leaf and stem
Figure 2: Grey Birch

Alder, Alnus rugosa
Small shrub 5′ to 20′ tall or a tree up to 40′. Bark dark brown and speckled with white streaks, twigs smooth to somewhat hairy, reddish-brown with scattered white lenticels. Buds blunt tipped, reddish- brown and stalked with two scales. Egg shaped, alternate leaves, dark green, hairless and wrinkled above, whitened, dull and somewhat hairy beneath. Margin double-toothed and undulating. Unisexual flowers; male catkin is 2″-4″ long and female catkin is 0.5″-0.75″ long. Nuts tiny and winged borne in a distinctive persistent cone-like structure. Prefers moist soils.

Alder
Figure 3: Alder
Alder leaf and stem
Figure 4: Alder

Willow, Salix spp.Shrubs or trees. Twigs slender with alternate, single scale buds pressed against the twig. Slender leaves 2″-7″ long and pointed, shiny and dark green above and paler beneath, margins toothed with short leaf stalks, prefers moist soils. Unisexual flowers borne in catkins on separate plants.

Willow
Figure 5: Willow
Willow leaf and stem
Figure 6: Willow

Red Maple, Acer rubrum
Multi-stemmed bush in the open with light gray bark and shiny, red, hairless twigs dotted with white lenticels. Leaves opposite with 3-5 lobes, 3″-4″ long with sharp angled lobes, dark green above and whitened underneath. Flowers appear in clusters in April, before leaf buds open. Male flowers, yellow-red, and female flowers bright scarlet, usually appear on separate trees. Prefers wetter soils.

Red maple
Figure 7: Red Maple
Red maple
Figure 8: Red Maple

Aspen, Poplar, Populus tremuloides
Twigs slender with scattered orange lenticels, slightly angled with buds shiny, hairless, dark brown and narrow. Smooth, grayish-green bark with whitish bloom. Leaves alternate, heart shaped, upper sides dark blue-green with underside a dull green. Flattened shape of petiole causes leaves to shake in the slightest breeze. Unisexual flowers, male and female catkins of about equal size appear on different trees.

Aspen
Figure 9: Aspen

Aspen

Figure 10: Aspen
Aspen leaf and stem
Figure 11: Aspen

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 1997, 2002

Published and distributed in furtherance of Cooperative Extension work, Acts of Congress of May 8 and June 30, 1914, by the University of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the USDA provide equal opportunities in programs and employment. Call 800.287.0274 or TDD 800.287.8957 (in Maine), or 207.581.3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit extension.umaine.edu.

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