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Plant Description


Betula alleghaniensis Britton

En: yellow birch, swamp birch
Fr: bouleau jaune, bouleau des All├ęghanys, merisier
Oj: wiinzik, wiggwass-zaawzi

Betulaceae (Birch Family)

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General: A medium to large hardwood tree, to 25-30 m tall, with large spreading branches. Bark reddish-brown when young, pale yellow to silvery-gray or bronze when mature and peeling (exfoliating) in thin papery curls. Twigs slender, brownish, slightly hairy (pubescent), and with the flavour of wintergreen when chewed. Terminal bud lacking on long twigs; lateral buds pointed, often pubescent, with 3 two-toned brownish scales. Short spur shoots have terminal buds with 5-7 scales.

Leaves: Alternate, simple, pinnately-veined, usually with 12-18 pairs of veins, petiolate. Leaf blade ovate, 6-10 cm long, 3-5.5 cm wide, widest just below the middle; upper surface dull, lower surface paler, hairy along veins and in vein axils; apex sharply pointed (acuminate); base rounded to slightly heart-shaped (cordate); margins double serrate. Leaves turn yellow in autumn.

Flowers: Unisexual, with male and female flowers occurring on the same trees (monoecious). Male flowers occur in pendulous catkins, 2 cm long at first, expanding to 8 cm long when pollen is shed. Male catkins are located near the branch tips while female catkins are positioned farther back on the twig. Each scale of the male catkin is associated with 3 male flowers, each with 2-3 stamens. Female flowers occur in erect catkins, to 2 cm long. Pistillate scales subtend 2-3 female flowers, each composed only of a pistil with a 2-carpelled, inferior ovary and 2 stigmas. Flowers bloom in early spring before the leaves emerge.

Fruit: The erect fruiting catkins are ovoid, 1.5-3 cm long, to 2.5 cm wide, with many, somewhat hairy, bracts (pistillate scales), 5-8 mm long, subtending the small dry fruits, which are winged nutlets. The 3-lobed pistillate scales have a narrowed base with 2 ascending lateral lobes and a central lobe of similar sizes. The thin, papery wings of the fruit are narrower than the nutlet. Fruits mature in late summer.

Habitat and Range: Yellow birch is found in rich moist deciduous and mixedwood forests; it is moderately shade tolerant. It is distributed throughout the temperate region of northeastern North America. In Ontario, its range extends north to about 48° N, divided into a northeastern and northwestern portion, separated by the north shore of Lake Superior.

Internet Links: The Betula alleghaniensis website from the USDA Silvics of North America website.

The Betula alleghaniensis webpage from the Trees of Wisconsin website.

Similar Species: Betula papyrifera (paper or white birch) can be distinguished by its bright white bark, which peels off in large, thin layers. Its twigs lack the wintergreen taste of yellow birch. The pistillate fruiting scales of paper and yellow birch also differ. Paper birch has pistillate fruiting scales with a pointed central lobe smaller than that of its 2 divergent lateral lobes, whereas yellow birch has scales with the ascending lateral lobes and central lobe of similar sizes. Yellow birch also has two-toned brown bud scales, while the buds scales of paper birch are green at the base and brown at the tip.

Yellow birch may also be confused with Ostrya virginiana (ironwood). The inflated involucres surrounding the small nutlets of ironwood are the most obvious difference, but Ostrya twigs also lack the wintergreen flavour and spur shoots characteristic of yellow birch, and have buds with several bud scales.

written by Derek Goertz and S.J. Meades

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