River birch (Betula nigra) is the most widely adapted of all the birches and grows throughout South Carolina. It is hardy in USDA Cold Hardiness Zones 4 to 9. River birch’s widespread popularity is widely attributed to the year-round interest of its peeling or exfoliating two-toned bark. On younger trunks and branches the pinkish to light brown bark curls and peels away in thin papery sheets to reveal lighter-colored, creamy tan to reddish-brown inner bark. On older trees, the bark becomes less showy and develops reddish- to grayish-brown to almost black scaly bark.
In the wild, river birch grows near the banks of streams and rivers, bottomlands, and floodplains throughout the eastern U.S., from eastern Pennsylvania and New Jersey to the Florida panhandle and as far west as southeastern Iowa, Oklahoma, and eastern Texas.
This deciduous tree typically grows 30 to 60 feet high and 20 to 50 feet wide. Young single-trunked trees have an oval to pyramidal habit that matures to a rounded crown. Multi-trunked trees (with an odd number of trunks)—considered the most attractive form—develop an irregular crown at maturity.
Expect river birch to grow at a medium to rapid rate (1 ½ to 2 feet per year), particularly in moist, fertile, well-drained locations in full sun to moderate shade.
In addition to the exfoliating bark that offers year-round appeal, river birch produces showy, reddish-green, 2- to 3-inch long male (staminate) flowers called catkins at the ends of branches. They appear in late summer and autumn and remain on the tree during the winter. In the spring, when the drooping, dark brown pollen-bearing male catkins expand and bloom, separate, greenish, ¾- to 1¼-inch long non-showy female (pistillate) catkins emerge from shortened shoots called spurs. These upright female catkins resemble small pine cones. Birch trees are monoecious, meaning that male and female flowers are produced in separate structures on the same tree. The wind-pollinated female catkins develop into brown, dangling structures that bear many small, brown, winged nutlets, which are dispersed by the wind.
The medium green, 1- to 3-inch long, triangular-ovate leaves turn pale shades of yellow in the fall.
Although river birch thrives in wet areas, it tolerates fairly dry soils once it becomes established. However, river birch tends to shed leaves and twigs during dry spells in late summer and early fall in response to drought stress. Maintain a 2- to 3-inch layer of mulch to conserve soil moisture. River birch requires acidic soils and may suffer from leaf yellowing, or chlorosis, caused by an iron deficiency at soil pH levels of 6.5 or higher.
River birch tends to “bleed” or exude sap when healthy live branches are removed in late winter or early spring. This leaking sap is not harmful—only unsightly. To avoid sap exudation, prune after the leaves have fully expanded in the spring to mid-summer or in early fall after the trees have shed their leaves.
Use river birch as a shade tree, as an attention-drawing specimen accent, or in a copse or group of trees. In naturalized landscapes, river birch thrives along stream banks and ponds. Choose a location that will accommodate its mature height and spread.
River birch has no serious pests. Fungal leaf spot diseases may result in early leaf drop during rainy summers. This typically occurs late in the season and usually is not severe enough to warrant fungicide applications.
River birch is resistant to bronze birch borer, a North American native insect that attacks white-barked birches, but is susceptible to the spiny witch hazel gall aphid. River birch is one of two hosts required by this aphid to complete its life cycle. In the spring, spiny witch hazel gall aphids that either overwintered as eggs on witch hazel bark (Hamamelis spp.) or as immature females beneath the birch bark feed on the sap of newly expanding river birch leaves. Their feeding causes the leaves to become distorted. The puckered or “corrugated” upper leaf surface produces deep channels on the lower leaf surfaces where the aphids feed; they are further protected by a coating of waxy-white granular material. After several generations, winged female aphids return to witch hazel to complete their life cycle.
Feeding by the spiny witch hazel gall aphids causes leaves to turn yellow and drop from the tree. Control is often unnecessary due to the minimal impact on tree health and the presence of numerous predators that manage aphid populations on birch leaves.
- ‘BNMTF’ (Dura-Heat®) –This heat- and drought-tolerant selection grows up to 50 feet tall and 30 feet wide with a dense broad columnar to oval-rounded crown. The peeling bark exposes creamy-white inner bark. Its leathery, lustrous dark green leaves, smaller than the species, turn yellow in the fall. Discovered as a seedling by Dwayne Moon of Moon’s Tree Farm in Loganville, GA.
- ‘Cully’ (Heritage®) – Extremely popular cultivar that grows faster than the species and has larger, glossier dark green leaves that are less susceptible to leaf spot. The large sheets of grayish-brown to tan flaking bark exfoliate to expose a tan to creamy-white to salmon-white inner trunk. At maturity, expect a height and width of 30 to 40 feet and 20 to 35 feet, respectively. Discovered in a St. Louis, MO suburb by Earl Cully of Cully Nursery, Jacksonville, IL.
- ‘Little King’ (Fox Valley®) – This dense, compact cultivar has a uniform, compact habit and grows 10 to 20 feet tall and 12 feet wide. The cinnamon-brown to pale salmon bark is similar to the species. Discovered and introduced in the late 1970s by Jim King of King Nursery in Oswego, IL, and in 1991 promoted through the Chicagoland Grows program.
- ‘Shiloh Splash’ (PP16,362) – This slow-growing (10 to 20 inches of growth per year) large shrub to medium-sized tree will mature to a height of 15 feet and develop a rounded crown. Variegated leaves are green in the center with brushstrokes of light green-yellow to creamy-yellow towards the edges on young leaves, while mature leaves develop white margins. Occasionally leaves will revert to wholly green and will have to be removed. The outer peeling trunk can be grayish-white to gray-orange, while the inner color is light reddish-brown to tan-brown. Discovered by John D. Allen in 1999 as a branch mutation (“sport”) growing on a seedling river birch tree of unknown parentage at Shiloh Nursery in Harmony, NC.
- `Studetec` (Tecumseh Compact®) – This compact cultivar with a rounded crown and drooping branches grows 10 to 15 feet tall with a spread of 15 to 20 feet. The exfoliating trunk and branches expose cinnamon-colored bark. Introduced by Studebaker Nurseries, Inc. in New Carlisle, OH.
- ‘Summer Cascade’ (PP15,105) – This weeping form grows 6 to 8 feet tall and 10 feet wide in 10 years. Grayish-white to gray-orange peeling bark reveals golden brown inner bark. Requires partial shade in the southeast. Originated as a seedling of unknown parentage that was discovered by John D. Allen of Shiloh Nursery in Harmony, NC.
- ‘WHIT XXV’ (PP16,573 City Slicker®) – The bark on this distinctive cultivar begins peeling at an early age when the stems are 1 inch in diameter to expose its creamy-white bark. It grows 30 to 40 feet tall with a 20 to 25-foot spread and develops a broadly pyramidal to oval crown. The dark green leaves turn yellow-gold in the fall. Resistant to leaf spots and is cold- and drought-tolerant. Selected by Carl Whitcomb, Ph.D., owner of Lacebark Nursery in Stillwater, OK, from river birch seed collected in central Oklahoma.
Note: Chemical control of diseases and insects on large trees is usually not feasible since adequate coverage of the foliage with a pesticide cannot be achieved.
References and Further Reading
- Chicagoland Grows® Plant Introduction Program: Fox Valley River Birch –Betula nigra ‘Little King’ (1991 introduction). 12 Jan. 2021. <http://www.chicagolandgrows.org/trees/riverbirch.php>.
- Clement, D. and M. K. Malinoski. 2009. IPM Series: Birch Trees. University of Maryland Extension Home and Garden Information Center. HG 58. 12 Jan. 2021. <https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/TreesandShrubs/HG58_2018_IPM_series_Birch.pdf>.
- Dirr, M. A. 2009. Manual of woody landscape plants. 2009. 6th ed. Stipes Pub., Champaign, IL.
- Dirr, M. A. and K. S. Warren. 2019. The tree book: Superior selections for landscapes, streetscapes, and gardens. Timber Press, Inc.
- Head, B. H. 2006. Hutchinson’s tree book: A reference guide to popular landscape trees. Hutchinson Pub. Corp., Taylors, SC.
- Grelen, H.E. 1990. Betula nigra L. River Birch Betulaceae Birch family, p. 153-157. In: R. M. Burns and B. H. Honkala (tech. cords). 1990. Silvics of North America. Vol. 2. Hardwoods. United States Department of Agriculture. Agriculture Handbook 654, Washington, D.C. 12 Jan. 2021. <https://www.srs.fs.usda.gov/pubs/misc/ag_654_vol2.pdf>.
- Hawke, R. G. 1991. Plant Evaluation Notes: The evaluation and introduction of a unique dwarf river birch. Issue 2. 12 Jan. 2021. <https://www.chicagobotanic.org/downloads/planteval_notes/no2_dwarfriverbirch.pdf>.