Betula lenta aka Cherry Birch

Sweet birch, Betula lenta, is a deciduous tree in the birch family, Betulaceae. Gardeners also know it as black birch, cherry birch or mahogany birch. It grows wild in eastern North America, from southeastern Canada and Maine south along the Appalachians. Its range reaches north Georgia and Alabama. It favours cool, moist forested slopes but also grows on rockier, more exposed ground.

In gardens the tree usually reaches 40 to 50 feet (12 to 15 m) tall, with a spread of 35 to 40 feet (11 to 12 m). Some sources give 60 to 70 feet (18 to 21 m), and wild trees can top 75 feet (23 m). Young trees are dense and pyramidal. With age the crown opens into a broad, rounded shape. It grows quickly when young.

Young bark is smooth, glossy and reddish-brown to almost black. Prominent horizontal lenticels mark it, much like cherry bark. On older trees the bark darkens and breaks into irregular scaly plates. Unlike many birches, it does not peel. Slender reddish-brown twigs smell of wintergreen when scratched or crushed. The simple, alternate leaves are ovate with a heart-shaped base and toothed edges. They measure about 2.5 to 6 inches (6 to 15 cm) long. In autumn they turn a dependable golden yellow, among the best fall colour of any birch.

Separate male and female catkins appear in spring, from about March to May, before or with the leaves. Male catkins are slender and yellow-green, up to about 3 to 4 inches (8 to 10 cm) long. Female catkins stand upright and are much shorter. Over summer they form small erect cones that break apart to release tiny winged nutlets. Birds eat the seeds. The tree also hosts caterpillars of the mourning cloak and dreamy duskywing butterflies, plus many moths.

Sweet birch grows best in rich, moist, acidic, well-drained soil in full sun or part shade. Full sun gives the strongest autumn colour. It copes with clay and shallow rocky ground, and it tolerates drier soil than most birches. It dislikes compacted soil, urban sites and hot, humid summers. Cool north- or east-facing slopes suit it well. It is hardy in USDA zones 3 to 8 and rated H7 in the UK. Prune only when fully dormant, since birches bleed heavily when the sap runs in spring. Use it as a shade tree, a lawn specimen in parks, or in naturalised woodland edges. Deer rarely browse it.

Like other birches, it can suffer from aphids, birch leafminer, birch skeletonizer and borers. Canker, leaf spot, rust, powdery mildew and honey fungus may also occur. Sources report good resistance to bronze birch borer. Its hard, heavy wood goes into furniture, flooring, cabinets and tool handles. The bark and twigs once supplied oil of wintergreen. People tap the sweet sap in early spring for drinks, syrup and birch beer. The dried inner bark can be ground and used as a famine food. Take care with the bark oil, though. It is almost pure methyl salicylate, which is highly toxic if swallowed and can be absorbed through the skin.