Identifying characteristics:
The young river birch has an oval to pyramidal outline, becoming broad-rounded
at maturity with a trunk that is often divided near the ground. It grows
40 to 70 feet tall, 40 to 60 feet wide and is often taller in the southern
states. Leaves are simple and alternate
on twigs but paired on spur shoots. They are 1.5 to 3.5 inches long, doubly
serrate and have wedge-shaped bases. The petioles are downy and the leaf
surfaces lustrous green above and finely hairy beneath. Fall color is a
dull yellow, and leaves drop early. Male flowers
are produced in slender, shiny, dark brown, pendulous catkins in mid to
late summer, opening the following spring. Female flowers are produced in
short, bright-green, erect catkins. The fruit
is a small, winged, nutlet borne on 3-lobed bracts in a pendulous, conelike
catkin. Seeds mature in May or June long before other birches, and fall
to germinate in the silt from spring flooding. The small leaf scars
are crescent-shaped with 3 bundle scars. The chestnut-brown buds
are ovoid, and covered with 3 or 4 sometimes hairy scales. Terminal buds
are only present on spur shoots. Bark
on young trees is thin, shiny and cinnamon-brown, peeling into papery, white
pieces to reveal the orange inner bark. Older trees have dark, reddish-brown,
almost black bark which is deeply furrowed and broken into scaly plates.
Similar species:
Ecology:
Distribution: This birch is the most widely-distributed native
birch in the US, occurring on moist sites from Massachusetts to northern
Florida, west to Minnesota and Kansas. It is common along the Mississippi
and Wapsipinicon rivers in eastern Iowa, and is widely planted throughout
the state.
Habitat: Usually found along stream banks and in swampy bottomlands, the river birch grows best in deep, rich, acid, moist soils, but also survives in drier soils. It withstands periodic flooding and is a medium to slow grower. It prefers a warmer climate than most birches and is the best choice for planting in hotter climates. This species is more reliably resistant to borers than the white-barked birches, and is cited as one of the most trouble-free birches. Leaf spot may sometimes cause premature defoliation and alkaline soils, especially in the Midwest, may lead to chlorosis.
Uses:
Wood: The wood is often knotty, reducing the value of this
tree for commercial timber. The wood is light brown, hard, lightweight,
close-grained and strong (but weaker than yellow birch). It is used occasionally
for inexpensive furniture, woodenware and tool handles. It was once used
for ox-yokes and wooden shoes.
Wildlife: Only of limited use to wildlife, the river birch produces abundant, tiny seeds which are eaten by turkeys, grouse, small birds and rodents. White-tail deer browse the young twigs and buds.
Horticulture: This species is valuable for sites which are wet for part of the year but dry in summer and fall. It transplants easily and is used for planting on estates, parks, campuses and other large areas, and for erosion control along stream banks. Multiple-trunked specimens are especially attractive for landscaping purposes. 'Heritage' is a vigorous cultivar with attractive bark coloration, is less prone to leaf spot, and is cold hardy to minus 40 degrees F.
