Paper birch

Description

Paper birch is a medium-sized, fast-growing, deciduous tree. It rises often on a single trunk, sometimes 2 or more trunks, from a shallow root system. It can reach up to 98′ tall and 32″ or more in diameter at breast height, though in Minnesota mature trees are usually no more than 60′ tall and 24″ in diameter. It is short-lived, usually surviving no more than 120 years, though older individuals can be up to 250 years old.

The trunk is slender, often curved, and often slightly leaning. It is distinct into the middle part of the crown or higher with few lower branches. The crown is pyramidal on young trees, narrowly oval and open on mature trees. The branches are ascending.

The bark on trees less than 5 years old is thin, smooth, and reddish-brown or orangish-brown, with conspicuous, pale, horizontal lenticels. On mature stems the bark is bright, creamy white with prominent, dark lenticels. The white bark is thin and peels in papery, horizontal strips. It often sheds in large sheets. The inner bark is reddish-orange. At the base of older trees the bark often becomes gray and deeply furrowed.

First-year twigs are slender and hairy at first, becoming dark reddish-brown with sparse, warty lenticels. Second-year twigs are hairless. Freshly cut twigs do not have a wintergreen odor or taste.

The buds are slender, 3 ⁄16″ to ¼″ long, tapered, and hairless. They are widest at the base and taper to a blunt point. The are covered with chestnut-brown scales that are often greenish at the base. They are covered with resin, making them gummy to the touch.

The leaves are deciduous and alternate. They are borne on shoots; 2 or sometimes 3 from a short, lateral shoot, and 1 from a longer shoot at the end of the twig. Each leaf is on a ⅜″ to 1″ long, usually hairless leaf stalk (petiole). The petiole is not flattened. The leaf blade is egg-shaped, 2″ to 4″ long, and 1¼″ to 2½″ wide. It is rounded, broadly angled, or nearly straight across at the base. It tapers to a point at the tip with straight or concave sides along the tip. The upper surface is dark green, dull, and hairless or nearly hairless. The lower surface is pale green and hairy along the main vein and in the vein axils. The margins are doubly-toothed with sharp, forward pointing teeth. There are 35 to 55 teeth per side. In autumn the leaves turn light yellow.

Male and female flowers are borne on the same tree and on the same branch. Male catkins are preformed in the late summer. They droop singly or in groups of 2 or 3 from the tips of leafless twigs, and sometimes from lateral shoots. They are ¾″ to 1″ long the first year, growing to 1½″ to 4″ long the following spring.

Female catkins appear singly on leafy, lateral branchlets on current-year twigs. They are ⅜″ to ¾″ long and erect.

The fruit is a cylinder-shaped cone containing many tiny, two-winged nutlets (samaras). It ripens in mid-August to mid-September. The nutlets are dispersed in the fall and early winter.

Height

40′ to 65′

Record

The champion paper birch in Minnesota is on private property near Hibbing, in St. Louis County. In 2023 it was measured at 55′ tall and 146″ in circumference (46½″ in diameter), with a crown spread of 62½′.

Flower Color

Green

Similar Species

Mountain paper birch (Betula cordifolia) leaf blade has a heart-shaped base.

Habitat

Moist to dry. Shade intolerant.

Ecology

Flowering

Late April to early June

Pests and Diseases

Birch-leaf blotchminer moth (Cameraria betulivora)

In 1988-89 Minnesota lost as much as 20% of its paper birch trees due to drought.

Use

Betula papyrifera is the state tree of New Hampshire.