Paper Birch
Betula papyrifera
Birch family (Betulaceae)

Description: This tree is 50-80' tall at maturity, consisting of either a single or multiple trunks and a narrow open crown (or crowns) with ascending branches. Some trees can have trunks up to 2' across. The bark of saplings and young trees is yellowish red, horizontally wrinkled, and shiny, while older trees usually have white bark with black horizontal wrinkles; this bark often peels into relatively wide ragged strips. There is an uncommon form of Paper Birch that has yellowish brown trunk bark even on mature trees. Large branches have bark that is similar to the bark of trunks, while twigs have reddish brown or reddish gray bark that is smooth. Young leafy shoots are green and glabrous to pubescent. The leaves are either alternate or they occur in groups of 2-3 on short spur-twigs. Individual leaves are 2-4" long, and 1-3" across; they are ovate to broadly ovate in shape and doubly serrate or serrate-dentate along their margins. The base of each leaf is rounded, truncate, or slightly cordate, while its tip forms an obtuse point. Each leaf has up to 9 lateral veins on each side of the central vein; the larger teeth of the margins are located where the lateral veins terminate. The upper surface of the leaves is medium green and glabrous, while the lower surface is usually pale green and glabrous to pubescent. The slender petioles are -1" long, pale green or pale yellow, and glabrous to finely pubescent. Paper Birch is monoecious, producing both male (staminate) and female (pistillate) flowers on the same tree; both types of flowers are organized into catkins. Premature forms of the catkins first develop during the fall, overwinter in a dormant state, and become mature during the spring as the leaves develop. Mature male catkins are 2-4" long, cylindrical in shape, and yellowish; they are usually arranged in groups of 3 and droop from the twigs near their tips. Each male catkin has numerous tiny flowers less than 1/8" (3 mm.) across; the male flowers are arranged in clusters of 3 behind tiny bracts. Individual male flowers consist of a tiny 4-lobed calyx and 2 stamens (there are no petals). Mature female catkins are 1-2" long, narrowly cylindrical in shape, and greenish; they are ascending, rather than drooping, and develop individually near the tips of twigs. On each female catkin, the female flowers are organized into clusters of 2-3 behind tiny bracts. Individual bracts have 3 upper lobes that are divergent and they are usually ciliate or pubescent. Individual female flowers consist of a naked ovary with a pair of styles; they are less than 1/8" (3 mm.) across. The flowers are cross-pollinated by the wind during the spring. Afterwards, the male catkins wither away, while the female catkins droop downward and become cone-like in appearance from the hardening of the bracts. The female flowers are replaced by small nutlets with lateral wings that are membranous and slightly wider than the nutlet. These winged nutlets are usually dispersed by the wind during the autumn; they can also be blown across the snow or transported by water. The root system is shallow and spreading. This tree spreads by reseeding itself. The deciduous leaves turn yellow during the autumn.

Cultivation: The preference is full or partial sun, moist to dry-mesic conditions, cool summer temperatures, and soil consisting of sandy or silty loam. This tree also adapts to upland areas with rocky soil, but its growth is stunted. Longevity of individual trees is 150 years or less. Outside of boreal areas with a cool climate, this tree tends to be short-lived.

Range & Habitat:
Paper Birch is an uncommon native tree that is found in northern Illinois (see Distribution Map). It is more common further to the north. Habitats include upland woodlands and savannas (often sandy or rocky), open disturbed woodlands, stabilized sand dunes near Lake Michigan, and riverbanks. Paper Birch is cultivated as an ornamental landscape tree. Paper Birch is a pioneer species that responds positively to disturbance, especially wildfires that damage dominant canopy trees.

Faunal Associations: The number of insects that feed on Paper Birch and other birches (Betula spp.) is quite extensive. The caterpillars of the butterflies Nymphalis antiopa (Mourning Cloak), Nymphalis vau-album j-album (Compton Tortoiseshell), and Polygonia faunus (Green Comma) feed on birches, as do the caterpillars of numerous moths (see Moth Table). Other insect feeders include the larvae of Croesus latitarsis (Dusky Birch Sawfly) and other sawflies, the larvae of Agrilus anxius (Bronze Birch Borer) and other wood-boring beetles, Polydrusus impressifrons (Pale Green Weevil), Altica betulae and other leaf beetles, Kleidocerys resedae (Birch Catkin Bug), the leaf-footed bugs Elasmucha lateralis and Elasmostethus interstinctus, Calaphis betulaecolens (Common Birch Aphid) and other aphids, and the leafhopper Erythridula praecisa (syn. Erythroneura praecisa). See the Insect Table for a more complete listing of these species. Paper Birch and other birches are used by vertebrate animals as a source of food, nesting or den habitat, and cover. The following birds eat the seeds of these trees: Black-Capped Chickadee, White-Winged Crossbill, Slate-Colored Junco, Common Redpoll, Fox Sparrow, Pine Siskin, and Passenger Pigeon (now extinct). The Ruffed Grouse and Purple Finch eat the buds and/or catkins, while the Yellow-Bellied Sapsucker drills holes into the thin bark of Paper Birch to suck the sap. The Ruby-Throated Hummingbird is a secondary feeder from these sap-holes. Other birds build nests on the branches or within the cavities of Paper Birch and other birches: these species include the Red-Breasted Nuthatch, Black-Capped Chickadee, Tree Swallow, several woodpeckers, and hawks. Strips of bark from Paper Birch are used by the Philadelphia Vireo and Black-Throated Green Warbler for nest construction. Various mammals also rely on Paper Birch and other birches to some extent as a source of food: the Red Squirrel eats the seeds and the Beaver gnaws on the wood, while the Cottontail Rabbit and White-Tailed Deer browse on the twigs and foliage, especially of seedlings and saplings.

Photographic Location: The Arboretum of the University of Illinois in Urbana, Illinois.

Comments: Paper Birch is widely regarded as an attractive tree, largely because of its white bark that often peels away into strips. While it may be tempting to pull on these bark strips and collect them as souvenirs, this impulse should be resisted as it damages the tree, causing ugly black scars to develop. Paper Birch has an unusually broad range across Canada and northern United States, which extends into the Appalachian mountains. Across this range, several varieties have been described that are not currently recognized in Illinois. Paper Birch is not the only birch species with attractive white bark. Two European species, Betula pendula (Weeping White Birch) and Betula pubescens (White Birch), are often cultivated as landscape trees in the United States and Canada. These species have white bark that is similar to Paper Birch, but their leaves are smaller in size (1-2" in length). A North American species, Betula populifolia (Gray Birch), also has whitish bark, but its leaves are more deltate in shape with long tapering tips.