January 2022 - River Birch
Common Name: River Birch. Alternate names include Red Birch, Black Birch, and Water Birch
Botanical Name: Betula nigra
Native Range: Eastern United States in Hardiness Zones 4 to 9, excluding mountainous areas and coastal plains (such as the NJ pine barrens). In nature it is found growing primarily in alluvial soils deposited by surface water in freshwater lowlands such as in the floodplains of rivers and streams.
Height: Usually 40’-70’, but can reach 90’
Spread: 40’-60’
Form: A gracefully branched deciduous tree, typically multi-trunked unless trained as a single trunk tree. Each trunk has a spreading crown comprised of several large, arching limbs which support slightly weeping branches.
Growth Rate: Vigorous, fast-growing. Over a 20-year period it may grow 30’-40’.
Sun: Full sun to part shade; intolerant of shade
Leaf Description: Simple, alternate, lustrous leaves, 1.5”-3.5" long, dark green above, lighter beneath, pointed at tip with wedge-shaped base and double serrated margins
Fall Color: Leaves turn a soft yellow and fall in late autumn.
Flower Description: River Birch is monoecious, with separate male and female flowers on each tree. Every fall, clusters of pendulous, 2”-3” long, brownish catkins form that contain the male flowers. In the following spring, in April to May, smaller, upright, greenish catkins with female flowers emerge. The matured male flowers release abundant pollen then, just as the tree is leafing out.
Fruit: Fertilized flowers develop into small tan or brown nutlets born in a 1”-1.5” thick, pendulous, conelike catkin. River Birch is the only spring-fruiting birch. Small winged seeds are shed in late spring or early summer, dispersed by wind or flowing water.
Bark Description: Younger trunks have a satiny gray-white and reddish-brown bark which exfoliates in papery sheets, revealing the variable colors of the underlying inner bark--shades of gray-brown, salmon-brown, cinnamon-brown, reddish-brown and occasionally white. Old trunks are reddish brown to grayish brown, deeply furrowed, broken into irregular plate-like scales.
Wildlife Benefit: River Birch is a food source for birds. More than 400 species of moths and caterpillars lay their eggs on birches. The result is bounty of caterpillars, the most important food for baby songbirds. In May and June the seeds of a River Birch attract a variety of birds – nuthatches, chickadees, titmice, sparrows, towhees, tanagers, grosbeaks, cardinals and finches. Songbirds also munch on the flower buds. Even in the winter woodpeckers are able to nab insects hiding under the birches’ peeling bark.
Tolerates:
- Prefers moist, acidic, fertile soils. Tolerates poor drainage. Despite its affinity for semi-aquatic conditions, it is only moderately resistant to flooding
- Classified as tolerant of deer. However, deer can browse its foliage, so new plantings may need protection until they grow taller than the browse line.
- Tolerant of clay soil, black walnut and air pollution.
Possible Insects: Although River Birch is host to several species of insects, it has no serious insect pests. It is extremely resistant to the bronze birch borer (Agrilus anxius) which is a problem for other birch species. It has limited susceptibility to aphids and leaf miner.
Possible Disease: Exceptionally disease-free, one of the most disease-free birches.
Uses:
- Valued as an ornamental tree. Its exfoliating bark can contribute significant winter interest to a landscape.
- Particularly suited for use in a rain garden, adjacent to ponds and streams, and in other wetland-prone areas.
- Its ability to thrive on moist sites makes it useful for erosion control.
Where to be found: Several are growing in the traffic island at the end of Battle Road Circle. Two older specimens may be found in the traffic island at the end of Evelyn Place. Single trunk specimens can be found in the Bank of America parking lot on Nassau Street.
River Birch can also be found naturally growing at Mountain Lakes. From Mountain Lakes House, walk down the right side of the lawn to the water. A trail will go off to the right. Take the trail and soon you will come to a little stone bridge that goes over a stream that flows down from upper reservoir to the larger central reservoir. Standing on the bridge, looking upstream, you will see river birch in the narrow thicket growing along the left side of the stream bank.
Additional Facts:
- Multi-trunked trees form a somewhat irregular crown, while single-trunked trees develop a pyramidal habit when young but mature to a more rounded shape.
- Avoid pruning in spring when the sap is running.
- May develop iron chlorosis in higher pH soils, so should be planted only in soils with pH 6.5 and below.
References
Missouri Botanical Gargen
https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277830#AllImages
Lady Bird Johnson Wildflower Center
https://www.wildflower.org/plants/result.php?id_plant=BENI
Martine, Christopher, Trees of New Jersey and the Mid-Atlantic States, Forest Education
Resource Center, NJ Department of Environmental Protection, 4th Edition, 2000
Leopold, Donald J., Native Plants of the Northeast, Timber Press, 2005.
North Carolina Audubon, “A River Birch Oasis,” https://nc.audubon.org/news/river-birch-oasis
Silvics of North America: Volume 2. Hardwoods, Southern Research Station, Forest Service, USDA https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_2/betula/nigra.htm
Dirr, Michael A. Manual of Woody Landscape Plants, Their Identification, Ornamental Characteristics, Culture, Propagation and Uses, 5th Edition, Stipes Publishing L.L.C., 1998.
Sandra Chen, December 2021
