River birch (Betula nigra)

Culture

Easily grown average, medium to wet soils in full sun to part shade. River birch is perhaps the most culturally adaptable and heat tolerant of the birches. Prefers moist, acidic, fertile soils including semi-aquatic conditions, but also tolerates drier soils. Consider using soaker hoses and bark mulches to keep the root zones cool and moist. Adapts well to heavy clay soils of Missouri and will tolerate poor drainage. Avoid pruning in spring when the sap is running.

Noteworthy Characteristics

Betula nigra, commonly called river birch, is a vigorous, fast-growing, medium-sized, Missouri native deciduous tree which occurs on floodplains, swampy bottomlands and along streams throughout the State. In cultivation, it can be trained as either a single trunk or multi-trunked tree. As a single trunk tree, it develops a pyramidal habit when young, but matures to a more rounded shape typically growing 40-70′ tall. Multi-trunked trees form a more irregular crown and are generally considered to be the superior growth habit for this species. Salmon-pink to reddish brown bark exfoliates to reveal lighter inner bark. Leathery, diamond-shaped, medium to dark green leaves (1.5-3.5″ long) with doubly toothed margins turn yellow in fall. Monoecious flowers appear in drooping, brownish male catkins and smaller, upright, greenish female catkins.

Genus name is the Latin name for birch.

Specific epithet means black.

Problems

One of the most disease-free birches. Most species of birch grow best in cool, northern climates, but do not adapt well to the hot summers of USDA Zones 5-9 and can be short-lived therein. Weakened birches become vulnerable to the bronze birch borer which typically infects and kills birches stressed by summer heat and humidity. River birches are Missouri natives that are naturally adapted to the climate and are extremely resistant to birch borer. Although river birches have some susceptibility to aphids, leaf miner and iron chlorosis in high pH soils, these problems are somewhat minor in comparison to the birch borer.

‘Heritage’ is a very popular river birch cultivar with superior ornamental features to the species (see Betula nigra ‘Curly’ HERITAGE).