Betula nigra, the black birch, river birch or water birch, is a species of birch native to the Eastern United States from New Hampshire west to southern Minnesota, and south to northern Florida and west to Texas. It is one of the few heat-tolerant birches in a family of mostly cold-weather trees which do not thrive in USDA Zone 6 and up. B. nigra commonly occurs in floodplains and swamps.
Description
Betula nigra is a deciduous tree growing to with a trunk in diameter. The base of the tree is often divided into multiple slender trunks.
Leaves and fruit
The twigs are glabrous or thinly hairy. There is an absence of terminal buds, and lateral buds often have a hook at the tip of the bud, which differs from other species in the family Betulaceae. The leaves are alternate, ovate, long and broad, with a serrated margin and five to twelve pairs of veins. The upper surface of the leaf is dark green in color, while the underside can be described as having a light yellow-green color. The leaves turn yellow in Autumn. The flowers are wind-pollinated catkins long, the male catkins pendulous, the female catkins erect. The fruit is unusual among birches in maturing in late spring; it is composed of numerous tiny winged seeds packed between the catkin bracts.thumb|River birch leaves & seeds
Taxonomy
Betula nigra is a tree that classified in the family Betulaceae, which is commonly known as the Birch or Alder Family. This family comprises six genera (Alnus, Betula, Carpinus, Corylus, Ostrya, and Ostryopsis) and includes alders, birches, hornbeams, and hazelnuts. Species within this family, along with Betula nigra, are shrubs or trees that grow along stream sides or in poorly drained soils throughout the Northern Hemisphere. Betulaceae is included within the order Fagales, which branches from the Rosid clade.
Habitat and range
The river birch is often found in low-elevation regions from as north as New Hampshire to as south as northern Florida. It can be found extending west to Kansas and east to the coast where proper habitat conditions occur. As its name depicts, this birch is found along stream-sides. It can also be a prominent species found in forested wetland communities and in areas containing moist soil, such as floodplains.
River birch is best placed in USDA hardiness zones 4–9.
Conservation status in the United States
It is listed as threatened in New Hampshire.
Ecology
In states in which mining is prevalent, the river birch is often used for reclamation and erosion control, as it is well suited for soils that are too acidic for other species of hardwoods. In West Virginia, they have been found to establish within mine refuse sites after being blown from neighboring areas.
Germination
Seeds are typically produced annually. Seasonal development begins in the fall as male catkins begin to form and mature. The emergence of female catkins corresponds with the return of leaves around early spring. Male and female fruit matures during the spring season or in the early summer months.thumb|Middle of the treeNative Americans used the boiled sap as a sweetener similar to maple syrup, and the inner bark as a survival food. The combined essential oils are phytotoxic to lettuce (Lactuca sativa) and perennial ryegrass (Lolium perenne) seedlings. They have also demonstrated insecticidal, nematicidal, and antibacterial properties.