Species distinguishing characteristics:
- Solitary, erect female catkins fall apart at maturity
- Oval- to heart-shaped, toothed leaves with pointed tips
- White to silvery-grey bark with horizontal, black lines
- Bark peels off in sheets
- Flattened nutlet with broad encircling wings
- Deciduous trees and shrubs with alternate, toothed leaves
- Male and female catkins on same tree or shrub
- Nutlets or winged seeds in cone-like catkins
- Family members include filberts/hazelnuts
- Often grows in the early successional stages after disturbance
Fast growing deciduous tree, 10–30 m tall, with trunks up to 75 cm in diameter. Rarely lives over 140 years. Highly varied growth and hybridizes readily with other birch species.
Leaves and stems:
One to several trunks. Slender branches, covered by leaf scars from previous years, angle upward on young trees and hang on older trees. Leaves, 4–10 cm long, are alternate, oval- to heart-shaped with pointed tips, and coarsely toothed edges. Leaves are flecked with black glandular dots on the underside and pale green and smooth on the upper side. Leaves turn yellow in autumn.
Reddish-orange or brown on young trees. Older trees have white to silvery-grey bark with long, narrow, horizontal lenticels or lines of raised pores. Peels off in strips to large sheets exposing reddish-orange inner bark that scars black. Old trees have deep black fissures on the base. The papery bark makes an excellent fire starter that can carry a flame even when wet. Collect only from downed trees as peeling bark from live trees causes permanent scars and can kill the tree.
Tiny flowers in long, slender, cylindrical clusters called catkins. Male (pollen) and female (seed) catkins, found on the same tree, flower before or with the emergence of leaves. Male catkins appear in the last joints of twigs in summer and stand erect during winter. In the spring they flower, lengthening to 5–10 cm, and droop. Female catkins, 2–4 cm long, are solitary at the end of side branches and stand erect at maturity. Greenish-yellow female flowers tinged with red become brown and almost woody after pollination.
Female catkins fall apart leaving only the core stem upon ripening of seeds. Oval seed, 2 mm, is a flattened nutlet much narrower than its encircling wing-like margin.
Moist, open to dense forests, floodplains and seepage, and disturbed areas at low to mid-elevations. Do not tolerate drought, shade, or saturated soils. Extremely frost tolerant.
Provides food for hoofed mammals (browse), birds (seeds and buds), and beavers (inner bark). Birch sap is used as a substitute for wintergreen oil and can be boiled down into maple-like syrup when tapped in early spring. Birch resin contains xylitol, a natural tooth cleaner. Boiled bark can be folded into baskets and water-tight containers. Birch canoes used by many tribal groups weighed 50 pounds and could carry 20 times their weight.
Birch trees are susceptible to damage from the bronze birch borer, a beetle that causes stunted or dead upper foliage and eventually death of the tree. Decline usually takes several years but can occur very quickly during a single hot, dry year. The reason for its current prevalence in our area is not well known. On the bright side, dead birches cycle nutrients and contribute organic matter to soil from its fast-decaying wood.