Description
Betula – Birch –
There are about 60 species of deciduous tall to medium sized trees and shrubs, which growth is initially fast, in this genus. They occur in diverse habitats, including woodland, moors, mountains, and heathland, throughout the Northern Hemisphere including arctic zones. They produce alternate serrated, usually ovate, mid to dark green leaves. Male and female flowers are borne in separate catkins on the same plant in spring, the male catkins are usually yellow-brown, pendent, and longer than the females, which are erect at first, becoming pendent. Birches are grown for their ornamental bark (glossy white or brown and/or peels off in paper like strips), colorful autumn foliage (usually gold), attractive male catkins, and graceful, open habit. Many are suitable for a small garden, either as isolated specimens or in small groups. They are usually shallow rooted. Bark was once used as paper by Ancient Buddhist and timber as use in the furniture trade. Sap and leaves are used medicinally as food or drink an as a dye
Grow in moderately fertile, moist but well drained soil in full sun or light dappled shade, but some adapt to poorer, shallower, even boggy soil.
Prone to various fungi including armillaria mealea and piptoporus betulinus that cause twig dieback. Also affected by leaf spots, viruses, anthracnose, rust, wood rooting fungi, borers (especially bronze birch borer), leaf miners, aphids, skeletonizers, leaf hoppers, caterpillars, gypsy moth larvae.
B. pubescens subsp. tortuosa – Downy Birch – This narrowly conical tree with densely ascending branches from Europe, Northern Asia, Greenland and Iceland grows 70′ feet tall and 30′ feet wide. It has a contorted dark brown trunk which has peeling bark with conspicuous horizontal lenticels, bark remains pale brownish cream to white at the base. It produces diamond shaped, sharply, unevenly toothed, mid green leaves, to 2 ½” long, turn yellow in autumn. In early spring it bears pendent, yellow-brown male catkins, to 2 ½” long, females are about a 1″ long. Tolerates poor or wet, acidic soils.
Zones 5-7
