Tropical Birch Trees
- The river birch (B. nigra) is the most heat-tolerant of all the birch species. This fast-growing tree grows 60 feet high and 40 feet wide and is often sold in clumps of two to five trunks. It has the characteristic weeping habit and fluttering leaves of all the birches. River birch is resistant to the bronze birch borer that decimates other types of birches in the South. River birches thrive along riverbanks and other wet areas in the eastern United States so plant them in full sun to partial shade in moist, slightly acidic soil. The river birch's most ornamental feature is its peeling, papery bark. "Heritage" is a commonly-sold cultivar with particularly showy bark and good disease resistance. B. nigra thrives in USDA Hardiness Zones 4 through 9 but struggles in arid parts of Zone 9 unless watered frequently.
- Also known as blue beech, ironwood and musclewood, the American hornbeam (Carpinus caroliniana) has oval leaves similar to those on birch trees, but the tree is more upright and rarely grows over 35 feet. Unlike the peeling bark on birch trees, the American hornbeam has smooth, blue-gray bark that does indeed resemble iron. American hornbeams are hardy in Zones 3 through 9.
- Another small member of the Betulaceae family, hophornbeam (Ostrya virginiana) is also called ironwood although the gray bark is ridged and scaly, not smooth as on American hornbeam. The tree has a graceful, rounded outline. It's tolerant of urban conditions and makes a good street tree. Hophornbeams are hardy in Zones 3 through 9.
- Don't be tempted to plant other birch trees in the South. Paper birch (B. papyrifera), black birch (B. lenta) and the European white birch (B. pendula) all grow well only as far south as Zone 6 or 7. Summer's heat and humidity can stress and weaken these trees, making them susceptible to a wide range of diseases and insects, especially the bronze birch borer. These birches rarely last long in the South, and those specimens that do require careful attention and lots of maintenance.
- While no type of birch tree grows in the tropics, river birches add grace and movement to sub-tropical home landscapes as well as commercial sites and parks. These easy-to-grow trees thrive in hot and humid areas, and their ornamental bark provides year-round interest.