Identifying characteristics:
This birch is most known for its gleaming, white trunk. It grows to 70 feet
tall or more, with a pyramidal crown in youth, becoming irregularly rounded
and relatively open at maturity. It often maintains a multi-stemmed habit.
On terminal twigs, leaves are
simple and alternate; on lateral branchlets, leaves are paired at the ends
of spur shoots. Leaves are 2 to 4 inches long, with doubly-serrate, coarsely-toothed
margins, and have hairy, 1-inch-long petioles. Leaf surfaces are smooth
and dull green above, with 3 to 7 pairs of lateral veins, and paler and
hairy on the veins below. Male and female flowers
occur in separate catkins on the same plant with or before the leaves in
spring. The hanging male catkins are brownish, and are borne in groups of
2 or 3. Female catkins are greenish and erect. Catkins are usually borne
at the tips of twigs and are visible during winter. The pendulous, conelike,
mature female catkins carry tiny, winged fruits
called "nutlets" borne between 3-lobed, deciduous bracts. Leaf
scars are small and semicircular, with 3 bundle scars. Terminal buds
are present only on spur shoots. Lateral buds are ovoid and 0.25 inches
long, with 3 or 4 smooth, chestnut-brown, imbricate scales. Young saplings
have thin, smooth, reddish to orange-tinted, creamy-colored bark which soon becomes bright, chalky-white,
peeling into papery strips. The bark becomes black and furrowed at the base
of old trees. This is the only native birch with white bark.
Similar species:
- European white birch (B. pendula)
- river birch (B. nigra)
- Japanese white birch (B. platyphylla var. japonica)
- quaking aspen (Populus tremuloides)
Ecology:
Distribution: Native to Canada, Alaska and the northern US, this
birch is one of the most characteristic trees of the northern woods.
It has the widest east-west distribution of all the native North American
birches. It is native to northeastern Iowa and on sheltered bluffs in Hardin
county along the Iowa River.
Habitat: Hardy from zone 2 to 6, this birch prefers cool, moist climates,
growing along lakes, streams, swamps and on uplands. It grows best on moist,
well-drained, acid, sandy or silt loams in full sun and is not suitable
for difficult sites or polluted areas. It is intolerant of shade and more
tolerant than the river birch
(B. nigra) to alkaline soils. It often seeds over mineral soils
exposed by fire. More resistant to bronze birch borer than the European white birch (B. pendula),
the paper birch often succumbs to this pest if planted outside its natural
range, and is generally susceptible to root rot. Birch dieback, a little-understood
disease, can cause heavy losses to paper birch and yellow
birch (B. alleghaniensis) populations. Paper birches are easily
damaged by fire, but usually resprout from the roots.
Uses:
Wood: Wood is close-grained, moderately heavy, moderately hard and
moderately strong. It is used for pulp, veneer, lumber, toothpicks, tongue
depressors and small, worked articles. It provides excellent firewood. Birch-bark
canoes of the Native Americans were made using the bark of this species
as it is strong, light and water-repellent. The bark is useful for lighting
fires when other materials are wet. Birch sap boils down to provide syrup.
Wildlife: This birch is an important tree to northern wildlife species. In winter, grouse eat the buds, and deer and moose feed on the twigs. Birds and rodents eat the seeds, and beavers relish the inner bark.
Horticulture: The paper birch is a fine specimen for use in landscaping in parks and large areas, providing attractive bark and good fall color. They are moderate to fast-growing but, like most white-barked birches, are short-lived in cultivation. Both the European white birch (B. pendula) and a cultivar of the Japanese white birch, 'Whitespire' show some resistance to bronze birch borer and are better choices for white-barked birches in most of Iowa.
