Birches are deciduous trees with scaly buds. Leaves are borne in an alternate pattern and are toothed. Flowers are monoecious and borne in catkins. Fruits are small, winged nuts borne in strobiles, or cones.
| I. | Leaves and 1-year-old twigs are aromatic when crushed. | |
| A. | One-year twigs and buds are glossy with a uniform, brown color. The bark of the trunk is glossy, smooth, and brown or black. Buds are somewhat pointed and sharp. Twigs are a source of the oil of wintergreen. | |
| Betula lenta–Sweet Birch | ||
| AA. | One-year-old twigs are gray to greenish-brown and lighter in color than the buds. Mature trunks have yellow, flaky bark. Buds are rather blunt and not sharp. | |
| Betula alleghaniensis (lutea)–Yellow Birch | ||
| II. | Leaves and 1-year-old twigs are not aromatic when crushed. | |
| A. | Leaves are glaucous (bloomy) beneath with seven to nine pairs of veins. Intermediate bark is tan to cinnamon-brown and exfoliates in papery flakes. | |
| Betula nigra–River Birch | ||
| AA. | Leaves are green beneath with three to seven pairs of veins per leaf. Foliage is triangular in shape. Bark on trunks is white and exfoliating. Branches are usually somewhat pendulous. | |
| Betula pendula (verrucosa, alba)–European White Birch | ||
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| Yellow Birch | |
Yellow Birch–Betula alleghaniensis (lenta)
The yellow birch is the most valuable birch of New England. In Ohio, it has been found locally in Ashtabula County, and south to Scioto and Adams counties. Yellow birch is often found in association with hemlock in Ohio. It requires the cool, moist soils of north-facing slopes.
The leaves are simple, alternate, and oval to oblong in outline. Foliage is 3—5 inches (7 1/2—13 cm) long. Foliage is dark green and lusterless on the upper leaf surface. Leaf margins are doubly and finely toothed. The leaf base is cordate. Fall color is an attractive yellow.
Overwintering buds are rather blunt and not sharp. The young twigs are light brown, lustrous, and slightly aromatic but less so than those of the sweet birch. The intermediate bark of the branches is silver or yellow with thin, papery layers separating and often curling at the edges, giving the trunk a ragged appearance. On large trees, the mature bark is made up of irregular, brown plates.
The flowers are in catkins. The male, or staminate, catkins are purplish and visible all winter, until they open in April or May. The female, or pistillate, catkins are greenish, erect, shorter, and thicker than those of the sweet birch and develop in the spring. Fruit is a cone with deciduous scales that matures in August or September.
The wood is heavy, strong, hard, and close-grained. The sapwood is light-colored, but the heartwood is dark red, which gives this wood the name of "red birch" to the lumber trade. The wood is used for flooring, woodenware, furniture, and other uses. It is prized as firewood.
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| Sweet Birch | |
Sweet Birch–Betula lenta
The sweet birch is also known as black birch or cherry birch and occurs in the coves and deep ravine pockets of the sandstone and shale formations of eastern Ohio. Its range extends from Ashtabula County southward to Highland and Adams counties. It attains its best development on cool, northerly exposures and on rich slopes where it reaches an average height of 70 feet and a diameter of 2—3 feet. The tree is moderately slow growing but is of value for its protection to the soil in the rugged sandstone cliff areas of eastern Ohio. When found growing in Ohio, it is usually associated with the hemlock forest.
The bark of the trunk is dark brown, almost black, dull, and broken into large, irregular, but not papery, plates. The small branches and twigs are glossy with a uniform, brown color that looks to have been polished. The twigs are very aromatic. Twigs are cut and distilled for the production of birch oil that is used as wintergreen flavoring. Buds are somewhat pointed and sharp.
The leaves are simple and alternately borne. Leaves are oval to oblong and 3—4 inches (7 1/2—10 cm) long. Foliage is dull and dark green on the upper leaf surface. Leaf margins are finely toothed. The upper leaf surface is glabrous with pubescent veins beneath. The leaf base is cordate.
The flowers are of two kinds. The male catkins are usually borne three to four on a shoot, form in the summer, and bloom the following April or May. Female catkins or "cones" open from mixed winter buds. The seeds ripen in late summer or autumn, and fall with the deciduous scales of the cone.
River Birch–Betula nigra
This is the only native birch found at lower elevations in the south. It is at home, as the name implies, along water courses and inhabits the deep, rich soils along the borders of streams, ponds, lakes, and swamps which are inundated for weeks at a time. In Ohio, it is limited to the southeastern portion of the state, extending from Fairfield County in a southeasterly fashion.
Young twigs are not aromatic when crushed. The bark provides a ready means for distinguishing this tree. Bark on 2—10-inch (5—25 cm) stems varies from tan to cinnamon-red in color and peels back in tough, papery layers. These layers persist on the trunk, presenting a very ragged and quite distinctive appearance. Unlike the bark of our other birches, the thin, papery layers are usually covered with a gray powder. On older trunks, the bark becomes thick, deeply furrowed, and reddish-brown in color.
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| River Birch |
The leaves are simple, alternate, and 2—3 inches (5—7 1/2 cm) long. The upper leaf surface is dark green and the lower surface is a pale, yellow-green. Leaves are glaucous (bloomy) beneath with seven to nine pairs of veins. The leaf margin is more coarsely toothed than the sweet or yellow birches. The leaf base is wedge-shaped.
The flowers are two kinds of catkins growing on the same tree. Male catkin buds are conspicuous in the winter but open with the female catkins in April or May. The fruit is cone-shaped, about 1 inch (2 1/2 cm) long, and densely crowded with little winged nutlets that ripen from May to June.
The wood is strong and fairly close-grained. It has been used in the manufacture of woodenware, in turnery, and for pulpwood. Since this tree is scattered in its distribution and mostly confined to banks of streams, it does not figure largely in commercial lumbering.
Recently, this tree has been heavily planted in Ohio's landscapes. All birch trees require acidic soil and are prone to developing an iron deficiency in alkaline soil regions. There is no practical control for the iron deficiency but to properly site this tree. Note that the natural range includes the acid soil regions of Ohio. A cultivar, ‘Heritage,' was selected for unusually light bark color and is popular. River birch is resistant to the bronze birch borer.
European White Birch–Betula pendula (verrucosa, alba)
A graceful tree, it is one of the most beautiful of the birches, planted quite extensively for lawn and ornamental purposes. Reaching heights of 40—60 feet with a wide, uniform crown, the European birch has slender, drooping branches. The European birch is not as well-adapted to Ohio landscapes as the native canoe or paper birch. Several horticultural types are planted including the cut-leaf cultivar (Betula pendula ‘Gracilis') with fine, deeply cut leaves.
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| European White Birch | ||
The trunk of the tree is short and rather stout. Bark is white on 2—10-inch (5—25 cm) stems and usually peels off in narrow, curly strips. The native canoe or paper birch has more colorful bark. Mature bark is deeply furrowed and almost black.
Leaves are 1—3 inches (2 1/2—7 1/2 cm) long with an acuminate leaf tip. Leaves are glabrous and dark green above and lighter beneath with three to seven pairs of veins per leaf. Foliage is more or less triangular in shape. The leaf base is wedge-shaped to truncate.
The bronze birch borer kills the European birch quickly in the landscape. Rarely does the European birch live more than five years in the landscape without an annual spray program. The paper birch has better bark color, but develops color one to two years later than European birch and commonly lives for 10—20 years without a spray program in Ohio. Because the bark colors later, the canoe, or paper, birch is less commonly grown in nurseries.