River birch bark flakes into sheets of creamy salmon pink to orange-red, with some cultivars providing a lighter-colored bark. Young saplings and twigs have smooth reddish bark, and on old trees the bark becomes brown and furrowed. The twigs are very fine and lend a delicate look to the tree in winter. The colorful bark stands out in the landscape, but it is just one great feature of the river birch.
River birch grows quickly to be a medium-height tree reaching 50-70 feet tall. It is much better adapted to hot summers than paper birch. It grows most commonly on the southeastern coastal plain, but can be found throughout most of the eastern United States. Although river birch does often grow along rivers in the wild, it can also be found on drier sites, making it well adapted to most home landscapes.
Plant river birch in full sun to part-shade. It prefers slightly acidic soils and the leaves may become chlorotic (turning lime-green in color due to iron deficiency) in alkaline soils. River birch prefers moist soils, but is drought-tolerant once established. Drought-stressed trees will sometimes lose their leaves early. River birch is resistant to bronze birch borer, an insect that attacks many other birch species. It has relatively few insect or disease problems. Most horticulturists recommend pruning river birch in summer or fall because sap flow in spring can be heavy.
River birch can be grown as a single or multi-trunked tree. The cultivar 'Little King' (Fox Valley?), is always multi-stemmed and grows only 10-12 feet tall. Plant river birch as a specimen tree or in a small grove. River birch planted next to a pond or stream will thrive and provide great wildlife habitat. The canopy of young trees has a pyramidal shape which becomes more rounded with age. Multi-trunk trees often develop an attractive, irregularly-shaped canopy.
The small, dark green leaves of river birch allow enough light through the canopy that river birch can be under-planted with many different shrubs and herbaceous plants. River birch stands out well when planted against a backdrop of evergreen trees such as holly or pines. Shrubs like Fothergilla, azaleas or rhododendrons can be planted under river birch. Ground covers that do well under river birch include wood asters, northern sea oats, and dwarf crested iris. River birch offers gardeners a great focal point in the landscape.
Article by Sylvan Kaufman. Dr. Kaufman is a writer of popular scientific and gardening articles. She is also an ecological consultant.
Photos Courtesy Missouri Botanical Garden PlantFinder