Trees & Shrubs of the Eloise Butler Wildflower Garden

River Birch is a forked, slightly leaning tree with an irregular crown. It grows to 80 feet in height.

The bark is smooth, ranging from creamy-white to shiny silver-ish to pinkish-brown and irregularly peeling into papery scales. The underside of the peeling layer is tinted red. With time, the bark becomes thick, fissured and shaggy with dark horizontal expanded lenticels.

Twigs are slender and very supple, reddish-brown and smooth to slightly hairy. Buds are slender and may be slightly hairy. There is no odor or taste of wintergreen when twigs are cut like there is with Yellow Birch.

Leaves are alternate, simple, ovate to almost 4-sided, about 1 to 3 inches long, with double saw-toothed edges, a stalked wedge shape base, shiny green on top and pale and fuzzy below, or at least on the mid-vein and there are often small resinous glands. Leaf stalks are hairy. Larger leaves will usually be shallowly lobed. There are usually 5 to 12 pairs of lateral veins. Dull yellow color in autumn.

Flowers: The tree is monoecious, that is with separate male and female flowers. Male flowers (staminate) occur in a cluster of 2 to 3 reddish-green hanging catkins, that appear near the ends of twigs in the fall and then elongate in the spring, up to 3 inches long. The individual flowers are only 1/8 inch long, are yellowish with 2 stamens, a 4-lobed calyx and are somewhat obscured by small bracts. Female flowers (pistillate) appear with the leaves and are greenish upright catkins, about 3/4 to 1-1/4 inches long, back from the tip on the same twigs as the male flowers, usually. They have an ovary, a pair of styles but no calyx or petals. Female flowers are in groups of three, obscured by a bract. Catkins are also referred to as 'aments'.

Fruit: Pollination is by wind. Female flowers mature to a short-stalked upright cylindrical non-woody cone, brownish in color with many hairy 3-lobed scales. The bracts of the flowers have become dry scales at maturity, each scale having three hairy 2-winged seeds (or nutlets) attached which disperse by wind and water in early summer to the following Spring. In moist soils the seeds germinate quickly. Young trees do not form seeds. Seeds are about 375,000 per pound.

Habitat: River Birch grows near water sources in moist rich soil, poorly drained or well drained. It has adapted to landscape plantings far from water and grows well if adequate moisture is provided. Full sun is necessary - it is not shade tolerant. It does not spread from its root crown, but will re-sprout from a stump. This species is sometimes subject to an anthracnose leaf blight.

Names: The genus, Betula, is the Latin word for the birch tree. The species, nigra, is the Latin word for 'black', and refers to the almost black color of old bark and therein begins a confusion in the common names. In the 19th century the species was sometimes named Betula rubra, which matches the alternate common name of 'Red Birch' and refers to the reddish tint of the exfoliating bark. The other alternate name of 'Black Birch' should not be applied as it is more appropriately used for the Sweet Birch, B. lenta, as it was in the 19th Century. Therefore, the name 'River Birch' has become accepted, which kind of agrees with the older name 'Water Birch', which was applied due to the affinity of the species to riparian habitats. The name 'birch' itself is derived from an old Teutonic word. The author name for the plant classification - 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.

Comparisons: The bark of River Birch exfoliates in a manner different from Paper Birch where the texture is more uniform and the exfoliation is a strip to a sheet. Also, the bark of Paper Birch, B. papyrifera, is whitish without the dark furrowing of older bark. See below for a leaf comparison.