T r e e s  o f  N o r t h  C a r o l i n a

Betula L. (Betulaceae)

A genus of 35-100 species of trees, shrubs, and subshrubs; of subarctic and temperate regions of the Northern Hemisphere. Section Betula (including the natives B. populifolia, B. papyrifera, and B. cordifolia) is widely distributed in the northern hemisphere. Section Costatae (including B. alleghaniensis, B. lenta, B. nigra, and B. uber) occurs in e. North America and e. Asia.

Six species occur in North Carolina, four are considered native to the state.

Key to Betula in North Carolina

1. Bark yellowish-gray, yellowish, pink, reddish-brown, or dark brown; samara rounded or slightly retuse at its apex, the wings making up 1/2 or less of the width; fruiting peduncles sessile (peduncled in B. nigra); [section Costatae]...2.

2. Inner bark of the twigs bitter, not aromatic; leaves cuneate at the base...B. nigra (River birch)

2. Inner bark of the twigs with odor and flavor of wintergreen; leaves rounded to subcordate at the base...3.

3. Bark of stems 5-30 cm in diameter (on larger trees look up for branches) yellow or yellowish-gray, exfoliating in papery shreds (bark of larger trunks becoming platey, the plates not prominently marked horizontally by old lenticels); scales of fruiting catkins 6-13 mm long, pubescent and marginally ciliate...B. alleghaniensis (Yellow birch)

3. Bark of stems 5-30 cm in diameter (on larger trees look up for branches) reddish-brown or dark brown, tight (bark of larger trunks becoming platey, the plates prominently marked horizontally by old lenticels); scales of fruiting catkins 5-7 mm long, glabrous...B. lenta (Sweet birch)

1. Bark white to pale gray; samara strongly retuse at its apex, the wings making up over 1/2 of the width; fruiting catkins peduncled; [section Betula]...4.

4. Leaves pubescent beneath, at least on the veins; bark of young stems exfoliating; leaf apex acute to short-acuminate; central lobe of infructescence scales equal to or longer than than the basal and lateral lobes. Leaves cordate with 6-12 lateral veins on each side of the midvein....B. cordifolia (Mountain paper birch)

4. Leaves glabrous beneath or somewhat pubescent on the veins; bark of young stems remaining tight; leaf apex long-acuminate to attenuate; central lobe of infructescence scales shorter than the basal and lateral lobes...5.

5. Leaf apex long-acuminate, but not attenuate; infructescence scales sparsely pubescent on the outer surface; bark of mature trees creamy to bright white...*B. pendula (European weeping birch)

5. Leaf apex attenuate-acuminate; infructescence scales densely pubescent on the outer surface; bark of mature trees grayish white...*B. populifolia (Gray birch)