River Birch

Size, growth and what to expect

River birch grows fast, typically 1.5 to 3 feet a year, and about 2.75 feet a year in our growth estimator. Expect 40 to 70 feet with a crown 40 to 60 feet wide, often on several trunks. The largest wild trees reach 100 feet. In dry city sites it may live only 30 to 40 years.

Catkins open in early spring, and the seed ripens and falls in May and June. Good seed crops come almost every year, and the seeds are the largest of any birch native to the United States. Grouse, wild turkeys, songbirds and mice eat them. The leaves turn yellow in fall.

It grows wild from eastern Texas and southeastern Iowa east to Virginia and northern Florida. Scattered stands follow rivers north to southern Minnesota, central Wisconsin and New England, and New Hampshire lists it as threatened. Its home is stream banks, sandbars and floodplains, where its seedlings come up in thickets on fresh silt.

How to grow River Birch

River birch wants full sun or part shade and a moist, acid soil, and it grows best near water. It takes clay, poor drainage and floods of a few weeks, but not water that stands all summer. Drought makes it drop its leaves, and on alkaline soil the leaves yellow. Its falling twigs clog gutters, so plant it 30 feet from a wall, and set trees 40 feet apart. Keep it more than 50 feet from overhead wires.

Saplings ship bare-root or potted. Plant them dormant, from leaf fall until bud swell, in a hole wider than the roots and no deeper. Set the root flare at the soil line, put the native soil back in, and spread mulch over the root zone, clear of the trunk. Pick the cones in May or June, while they are still green enough to hold together. The seed needs no chilling. Sow it at once, or in spring, on the surface of moist soil, barely covered, since light helps it sprout.

Water deeply through the first two summers and in dry spells after that, since it needs a moist soil. A thick mulch keeps the roots cool and moist. Deer browse the twigs and leaves, so cage young trees. Prune only in summer or fall, since a birch cut in late winter or spring bleeds sap.

Male and female catkins grow on the same tree, and the wind carries the pollen. River birch sets almost no good seed with its own pollen, so plant two or more seedlings if you want seed. It resists the bronze birch borer, which kills many other birches. Aphids can be bad in early spring, the spongy moth favors its leaves, and leaf miners and leaf spots show up in some years.