River birch is the southernmost and, perhaps, preeminent birch species in the United States. Its flaky, pinkish-brown bark and shimmery foliage enchant all who gaze upon the tree, and the dreaded bronze birch borer likewise succumbs to the spell, moving on to another species while leaving river birch unscathed. River birch grows rapidly up to 60 feet tall in full or part sun and moist to wet, acidic soils, thriving in sites located alongside bodies of water or in occasionally flooded bottomlands. While it's able to tolerate drier soils and alkaline or neutral pH, these conditions often result in leaf drop and chlorosis of the foliage and should be avoided, if possible. Keeping the foliage healthy and intact is important not only for their ornamental value--lustrous green in summer and bright yellow in fall--but also for their ecological impact: the leaves of genus Betula nourish over 300 species of caterpillars. Moreover, numerous birds, waterfowl, and small mammals eat the tiny winged seeds and use the tree for nesting and cover.
River birch is native to the eastern and southern states, the lower Midwest, eastern Great Plains, and lower Mississippi River Valley. In Ohio, it grows mostly in the south-central counties and sparsely along Lake Erie. However, it is widely planted throughout Ohio and the eastern US as an ornamental shade tree, and it's often used in erosion control.
According to the Ohio Department of Natural Resources, river birch trees that occur in the wild usually have excessively flaky, dark gray to black outer bark with subtle orange and cream markings on the inner bark. Selections have been made by humans that have brilliant orange, cream, and near-white peeling bark on both the young and mature trunks and branches, making this birch the easiest of all to identify, especially in winter.
Native habitats include thickets along rivers, streams and lakeshores, flood plains and low-lying areas. Because of its broad root system, river birch is great for preventing erosion, but it is best sited a good distance from buildings.
Plant Characteristics:
Grows to 40-60’ tall at a medium to fast growth rate.
Grows best in full sun and doesn't tolerate shade. Tolerates very hot summer weather and occasional drought.
Prefers rich, medium to wet, acidic soils, including loamy, gravelly, silty, and clay, but tolerates drier soils once established.
Male catkins develop at the tips of twigs in clusters of 2-3; they are 2-3" long, reddish yellow, narrowly cylindrical in shape, and slightly drooping. Female flowers are about 1/8" long. Female catkins turn brown and develop a cone-like appearance. The resulting winged seeds are broadly ovate, tapering to a slender beak. They are dispersed by water and wind in late spring.
Alternate leaves are 2-3" long and 1½–2¼" across; they are ovate-deltate shaped and doubly serrated along the middle to upper margins. Leaf bases are broadly wedge shaped. Upper surface of the leaves is medium to dark green and glabrous, while lower surface is either pale or whitish green and glaucous.
The trunk bark of young trees exfoliates extensively, becoming ragged with patches of reddish brown, dull orange, or pinkish tan. Older trees have gray-brown, scaly bark that exfoliates only slightly. The bark of branches and twigs is smoother and grayish brown.
The root system is woody and branching.
Reproductive System: male and female flowers are on separate catkins on the same plant (monoecious). Individual plants are self- or cross-pollinated by the wind and other birches.
Wildlife Value:Host plant to 317 species of moth and butterfly larvae, including the wavy-lined emerald (pictured here), pale beauty, and dreamy duskywing moths. Numerous terrestrial birds and waterfowl use this tree for cover and nesting, and several waterfowl, wild turkey and other bird species enjoy the seeds. Hummingbirds are as attracted to the sap as they are to the small insects that often become stuck in the sap. Resistant to the bronze birch borer.
Medicinal, Edible, and Other Uses:
Native Americans boiled the sap to make syrup. The bark was boiled to treat digestive disorders and urinary difficulties. The leaves were chewed or made into tea to treat colds, dysentery, and urinary issues. Skin sores and ringworm were treated with a salve that was made by boiling the buds until they were thick and pasty, then adding sulfur and applying externally.
The wood is hard, strong, and close grained, but it's too knotty for use in lumber. Its main uses are for local furniture manufacturing, basket materials, small woodenware, and fuel. Its light weight also makes it suitable for artificial limbs and toys.
Resources:
Illinois Wildflowers
Ohio Department of Natural Resources
https://ohiodnr.gov/discover-and-learn/plants-trees/broad-leaf-trees/river-birch-betula-nigra
United States Forest Service
https://www.fs.usda.gov/database/feis/plants/tree/betnig/all.html#40
