HARDINESS: Zones 4 to 9
PREFERRED SOIL pH: Acid
PREFERRED SOIL TYPE: Moist, sandy soil
PREFERRED LIGHT: Sun
ATTRIBUTES: Attractive bark, open canopy; for specimens, foundation plantings
SEASON OF INTEREST: Year-round
FAVORITES: B. nigra 'Heritage', 'Little King'; B. papyrifera; B. pendula
QUIRKS: Drops small twigs and leaves that require raking
GOOD NEIGHBORS: False cypress, pines, red-osier dogwood, winterberry holly, viburnums
WHERE IT GROWS BEST: Moist soil and full sun
LONGEVITY: Lives many years
POTENTIAL PROBLEMS: Aphids, borers; leaves turn yellow when trees are grown in alkaline soil
SOURCE: Nursery plants
DIMENSIONS: 40-70 ft (12.2-21 m) tall and to 30 ft (9.1 m) wide
River Birch in the Landscape
A highly desirable landscape tree, river birch is famous for its ridged, ruddy brown bark that peels, revealing shaggy, salmon flakes. It also has a rounded crown, topping out at 40-70 ft (12.2-21 m). Its small, diamond-shaped, green leaves flutter in the breeze, creating a light, airy effect. In fact, the canopy is so open that you'll have no trouble growing bulbs, annuals, and groundcovers at its base, where they'll receive ample light.
As its common name suggests, river birch is found in lowland areas where the soil is often saturated. Its adaptability to poorly aerated sites also gives it an advantage in gardens with compacted soil. Hardy to Zone 4, river birch equally at home in extreme summer heat. This is the perfect tree for urban areas or a new garden where fast growth and sun tolerance are important. River birch makes a lovely specimen or a graceful marker at the corner of a house.
Popular River Birches
For added drama, look for the variety 'Heritage', whose bark peels in large, tawny orange patches instead of small, curly flakes. It is also tolerant of dry soil and resistant to pests. 'Heritage' is very easy to find and is often the only river birch carried at nurseries. A classy dwarf called 'Little King' is also becoming popular. Standing 20-25 ft (6.1-7.6 m) tall, this variety develops a tapered trunk and is in scale with small landscapes.
Other Care-Free Birches
Another birch with peeling bark is paper birch (B. papyrifera), which grows to 100 ft (30.5 m).This birch earned its name from the silvery to creamy white bark that curls into little tubes, like rolls of paper. Hardy to Zone 2, it is not dependable in extreme summer heat, which also makes it vulnerable to pests. European white birch (B. pendula), has silvery white peeling bark when young, but the trunk turns dark
with age. The branches are droopy, creating a soft crown atop a 40 ft (12.2m) tall tree. It tolerates drier, less acid soil than other birches and is hardy to Zone 3. 'Purpurea' and 'Purple Splendor' have purplish leaves, and 'Youngii' is a smaller, weeping variety with a mushroom shape.
Growing River Birch
Transplant river birch in early spring. It will establish quickly, growing up to 3 ft (1 m) annually in loose, sandy, acid soil if kept moist in droughts. Yellowing leaves indicate alkaline soil. Amend soil with garden sulfur, per label, to neutralize the soil pH. Dry soil reduces vigor, making trees susceptible to borers, which are small caterpillars that bore holes into the trunk, seriously weakening the plants. It pays to irrigate as needed and lay a 3 in (7.6 cm) layer of mulch to reduce evaporation from the soil.
River birch requires no pruning, but it drops small twigs and leaves, which do require periodic raking. Occasionally river birches become infested with sap-sucking insect aphids. Spray aphids off foliage with water from a hose, or apply an insecticidal soap formula that also contains citrus compounds, per label.