The river birch (betula nigra) is a tree native to the South and eastern U.S. that is a popular ornamental choice. (Special photo)
“A lady like a river birch spreads seeds by seizing wind — while some may cling to weathered arms, still more wait deep within. … She’ll sprout new leaves in springtime, she’ll shade the summer sun, she’ll rustle in the autumn breeze, ‘til winter’s song is sung.”
— Joy A. Burki-
Watson, “The River Birch”
Betula nigra (river birch or water birch) is a species of birch native to the eastern and southern United States. It is a deciduous tree commonly found in the flood plains and swamp areas growing upwards to 80 feet with a two-foot trunk (often multiple trunks). The bark of the river birch is usually dark gray-brown to pinkish-brown and scaly. And in some situations it appears smooth and creamy pinkish-white with exfoliating curly papery sheets. The flowers are wind-pollinated catkins with the male as pendulous and the female as erect. The fruit matures in the late spring and consists of numerous tiny winged seeds positioned between the catkin bracts.
While its native habitat is a wet, lower environment, the river birch will grow on higher elevations. Its bark is very distinctive, thus making it a favored ornamental tree for landscape uses. Several cultivars with whiter bark than the typical native type have been selected for landscape planting including Heritage and Duraheat. Also, these two are recognized as the only white-barked birches tolerant of the bronze birch borer (Agrilus anxius) in warmer areas of the southeast.
The Native Americans used the boiled sap of the river birch as a sweetener (similar to maple syrup) and the inner bark for survival food. It has little value as a timber tree due to its contorted and knotted growth features and lack of uniformity in wood grain. However, its wood is locally used for fuel and occasionally inexpensive furniture, as well as oxen yokes, wooden shoes, basket hoops, artificial limbs and toys. Also, it was once used instead of hickory to make rice casks.
The cinnamon-colored, exfoliating bark of the river birch is awesome in appearance during the winter months (fall leaf color is golden yellow). During the growing season it exhibits lustrous, medium-green leaves (silvery white underneath) and tolerates wet soils and dry summers. It does not tolerate shade and prefers slightly acid to neutral and moist soil conditions. The river birch is the most common birch tree found in our area, since most birch species prefer the cooler climates to the north. It is a fast-growing tree but its life is short compared to most trees.
The bark of the river birch varies according to its age as young trees have a silvery gray bark with light reddish-brown patches and the older trees have dark reddish-brown bark (almost black). It has two different flowers with the male flowers growing in the fall, remaining on the tree through the winter, and producing pollen in the early spring. The female flowers grow in the spring and turn into fruit in May and June (cone filled with hairy seeds) after pollination and are dispersed by wind and water. The ripening of seed coincides with high water levels of rivers (its native setting) thus allowing the seed to be carried long distances by the water. The seed germinates quickly in the mud thus allowing it to grow in areas where it helps prevent erosion.
In such natural settings, the river birch usually grows close to water and is often found on sandbars, islands in streams, streambanks, lakeshores and floodplains. Other trees found growing in nature in the vicinity of the river birch include American sycamore, red maple, silver maple, black willow, American hornbeam, yellow poplar, blackgum, black cherry, American elm, sugar maple, boxelder, mockernut hickory, American beech, ash, sweetgum and pin oak.
The river birch is one of the most recognizable and beautiful trees in the landscape. It sheds its bark constantly which drops underneath the tree as a beneficial mulch thus preventing aggressive competition from weeds and other unwanted plants. It is much more resilient and heat tolerant than the white paper birch and is very popular for landscaping on estates, golf courses, metropolitan locations, small business locations, recreational areas, parks, and homes. The river birch is a very popular lawn tree which thrives easily in hot, humid locations and exhibits the attractive peeling bark feature. As one of the fastest growing and outstanding shade trees, it can offer energy savings through temperature control thus lowering your electricity bill as an added bonus.
The river birch can be purchased as a multi-trunk shade tree, although the single trunk specimens are most preferred. It can be used as a screen or shade tree, and as a street tree with irrigation. They are attractive when planted in groupings, especially against a dark background. Because of its shallow root system, the river birch is easy to transplant. It should be pruned during the summer to minimize excessive sap bleeding which can result from spring pruning.
The cultivars include Cully (a broad pyramidal with lighter bark than the species and large, glossy green leaves offering a good resistance to bronze birch borer) and Heritage (a heat-tolerant, highly adaptive cultivar with larger, glossier leaves). The Royal Horticultural Society labels Cully as Heritage and is sold under the name of Heritage, even though many distinguish it as an independent cultivar.
Heritage received a Pennsylvania Horticulture Society Gold Medal in 1990 and was selected as 2002 Tree of the Year by the Society of Municipal Arborists. The bark of Heritage is whiter than any birch resistant to bronze birch borer. Heritage offers many positive traits including a cold tolerance in northern environments and a tolerance to the heat of the southern environments.
Other cultivars include Duraheat (glossy dark green, closely spaced leaves with yellow fall color, aphid resistant, and bark exfoliation at early age), Fox Valley (a dense, compact, oval to rounded habit with branches to the ground and dense foliage) and Suwanee (lustrous dark green leaves with salmon white exfoliating bark). Avoid those selections that exhibit growth patterns not consistent with the species including variegated leaves and weeping growth habits.
The river birch is a sustainable landscape tree with showy bark and very favorable for the environment exhibiting interesting features throughout all seasons. As a fast growing and adaptable tough tree, Heritage is an excellent choice as a shade tree for all sizes and shapes of landscapes and gardens.
As you continue your sustainable plantscaping this month and commit to this cost and effort, please also commit to providing the necessary care to keep your plants healthy and attractive. And, as always, remember to feed and water the birds!