Betula nigra L. River birch, red birch. Family Betulaceae. ITIS Taxonomic Serial Number 19480. USDA PLANTS Symbol BENI. TROPICOS # 03600067.
Images Branchlet with leaves. Individual leaf. Branchlet with pistillate flowers. Branchlet with buds and staminate catkins. Close-up of bud and staminate catkins. Herbarium sheet 1. Herbarium sheet 2. Herbarium sheet 3. Herbarium sheet 4.
Brief Description: A small to medium-sized, deciduous tree, commonly ranging from 1525 m (5080 ft.) tall when mature. Bark is salmon-pink to creamy white, tan, grayish brown or reddish brown and separating in irregular sheets, becoming dark brown and furrowed on older trees. Leaves are alternate, relatively small (mostly 48 cm long), and more or less arrowhead shaped. The leaf margins are variously toothed, except for the base of the leaf blade, which is entire. Flowers are arranged in separate male and female catkins that occur on the same tree, the dangling male catkins forming during the summer and persisting on the tree through the winter. Fruits are brown or tan, small (37 mm long) samaras that are borne in dense, cylinder-shaped structures that look like cones. (Botanically, however, these are not cones since, unlike the conifers, the seeds are produced by small flowers.) River birch is common along the rivers and streams of the Piedmont, sometimes hanging far out over the water. Easily recognizable by its exfoliating or roughly furrowed bark.
Plant habit and life style. Plants Angiosperms, monoecious, (10)1525(30) m tall.
Stems. Pith continuous. Young twigs (1-year-old or less) red or reddish-brown, glabrous or glabrate or pubescent. Twigs (24 years old) glabrous. Leaf scars crescent-shaped or half-round or triangular, bundle scars 3 per leaf scar, stipule scars present or inconspicuous, short shoots present, short shoots bearing leaves. Bark of mature trunks with conspicuous lenticels or exfoliating or furrowed or shreddy.
Buds. Buds axillary, reddish-brown, (4)57 mm long, ovoid or ovoid-conic, sharp, glabrous or glabrate or pubescent, ciliate or puberulent or tomentose, bud scales imbricate.
Leaves. Leaves deciduous, simple, petiolate, alternate or spiral, (3)48 cm long, (2.5)36 cm wide, deltoid or ovate or rhombic, leaf margins dentate or serrate or doubly serrate, leaf apices acuminate or acute, leaf bases cuneate or obtuse or truncate. Leaf upper surface green, glabrous or glabrate or pubescent, tomentose. Leaf lower surface green or white, glabrate or pubescent or with tufts in vein axils, tomentose or villous. Leaf venation pinnate, secondary veins on either side of the midvein 512. Petioles 0.32 cm long, pubescent. Stipules present, caducous, scarious.
Flowers. Flowering February or March or April. Inflorescences terminal, catkins or cymes or simple dichasia, flowers sessile or stalked. Flowers unisexual or pistillate or staminate, epigynous. Perianth. Calyx synsepalous. Sepals (2)4(6) per flower. Corolla absent. Androecium. Stamens (1)2(4) per flower, separate. Gynoecium. Ovaries inferior, pistils 1 per flower. Gynoecium syncarpous, 2 carpels per flower, styles 2 per pistil, placentation apical. Other floral features. Hypanthia present.
Fruits. Fruits nuts or samaras, 0.30.7 cm long, brown or tan, fruit maturation 1 years.
Habitat. Habitat bottomland forests or disturbed and weedy areas or mesic upland forests or mixed forest edges or suburban plantings.
Special Diagnostic Characters. Mature bark salmon-pink to creamy white, tan, grayish brown or reddish brown and separating in irregular sheets, becoming dark brown and furrowed; base of the leaf blade entire, the upper portion variously serrate or dentate; the small fruits borne in dense, cylinder-shaped, cone-like structures, 1.54 cm. long.
Cite this publication as: ‘Stephen M. Seiberling, Alan S. Weakley, and Peter S. White (2005 onwards). Common Trees of the North Carolina Piedmont: Identification, Descriptions, Illustrations, and Glossary. Version: March 7, 2006. <http://www.ibiblio.org/openkey/intkey/>’.
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