The decision to plant a river birch tree in the woodland section of my garden was a convoluted one as I went back and forth while considering many species for this particular spot. I wanted something that took up space without excessive height, and something ornamental, even striking. I thought seriously about a camperdown elm, a magnolia, a Cornus kousa, and a weeping katsura. But when I visited the Connon nursery lot and saw a group of multi-stem river birches, they arrested me. I decided on the spot that I must have one, and I couldn’t be more pleased with the way this tree looks in my garden. I took this photo on October 20, 2020, a few days after it was planted with four other trees on October 16. With most of its leaves gone, the exfoliating bark stands out, a key feature of this exquisite tree. Somehow, nothing suggests a woodland as much as a birch.
Virginia Tech Dendrology describes the tree like this:
Leaf: Alternate, simple, pinnately-veined, rhombic to ovate, 1 1/2 to 3 inches long, conspicuously doubly serrate, with a wedge-shaped base, green above, paler and fuzzy below.
Flower: Species is monoecious; preformed, reddish green, male catkins near the end of the twig, 2 to 3 inches long; female catkins upright, 1/4 to 1/2 inch long, light green, appear or elongate (males) in mid-spring.
Fruit: Cone-like, aggregate, 1 to 1 1/2 inches long, with many hairy scales, reddish brown, containing many tiny, 3-winged seeds, ripen and break apart in the fall.
Twig: Slender, orangish brown in color, smooth or slightly pubescent, with the terminal bud absent. Lateral buds may be slightly pubescent. No wintergreen odor when cut.
Bark: Smooth on young trees, salmon to rust colored; developing papery scales, exfoliating horizontally with several colors (creamy to orangish-brown) visible; later developing coarse scales.
Form: Medium size tree reaching up to 70 feet tall. The trunk generally divides low into several upright trunks.
Missouri Botanical Garden, describes Betula nigra as “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.”
The river birch is native to North America, but its range “may be expanded by planting,” presumably to Canada. My friend, Sarah Elias-Hacon, had one in the front of her townhouse in the Kingston co-op where I stayed while teaching for many years. I had always admired it. The North American Native Plant Society does not list it as a tree native to Canada. Missouri Botanical Garden notes that the tree is native to Missouri.
Hardy between zones 4 to 9 the tree reaches a height of 40 to 70 feet and a spread of 40 to 60 feet, its bloom time between April and May. Its maintenance needs are low. The tree needs full sun to part shade, medium to wet conditions, and moist, acidic, fertile soils including semi-aquatic conditions. Tolerant of deer, drought, clay soil, wet soil, black walnut, and air pollution, it attracts birds, an observation I can confirm from peering out my back window. Sparrows discovered it the week is was planted and while the thinning foliage provided no concealment, they nonetheless seemed to enjoy flocking to its branches.
One reason I had hesitated was my understanding that birches are relatively short-lived trees with susceptibility to infestation by the birch beetle. I have since learned that Betula nigra has more natural immunity against the beetle, and is generally hardier and more adaptable to sandy soils like the kind we have in Toronto’s east end. Missouri Botanical Garden notes that “river birch is perhaps the most culturally adaptable and heat tolerant of the birches.” One of the most disease-free birches, the river birch adapts to hot summers of zones 5–9 better than other birches. “Weakened birches become vulnerable to the bronze birch borer which typically infects and kills birches stressed by summer heat and humidity…River birches 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.” I will have to keep my eye on the tree to prevent any onset of these pests and diseases even though I have no reason to expect that my soil is high in pH.
For optimal care of the river birch, bark mulch is recommended to keep the root zones cool and moist. Avoid pruning in spring when the sap is running.