Family: Betulaceae
Common Name: Birch

There are about 60 species of birch, all of which are deciduous trees or shrubs native to the northern hemisphere. Birches play a rich role in the folklore of the northern Europeans and the indigenous peoples of North America, although many beautiful species are also native to China and the Himalayas. Many species have a long history of usage, some of which continues today. Mostly slender and graceful, the birch is one of the most popular ornamental trees. They have small, heart-shaped, vivid green leaves, with fine stalks. Some of the species are grown for the quality and colour of their bark, which may take several years to develop, and for their golden autumn leaves. Quick-growing in the early stages, they reach heights of 7-18 m (23-60 ft), but are still suitable for smallish gardens because they do not spread too widely. However, birches look their best when planted in groups.

Species

B. nigra, river birch, grows in a pyramid shape to 15 m (50 ft) and is suitable for zone 4. It does well on the banks of rivers and lakes, its natural habitat in North America. The mature trunk is rugged and blackish, while the young trunk is much lighter in colour.

B. papyrifera, canoe birch or paper birch, zone 1, also from North America, reaches a height of 15 m (50 ft) and has white papery bark which peels off to reveal pale orange-brown bark.

B. pendula, European or silver birch, zone 2, is the most commonly grown species and one of the most elegant. It has attractive silvery white bark and small, bright green leaves which turn gold in autumn. B. pendula cultivar 'Dalecarlica', cut-leaf birch, from Sweden, reaches a height of 10 m (33 ft) and has unusual deeply lobed leaves. Cultivar 'Fastigiata', upright silver birch, is column-shaped. Cultivar 'Purpurea', purple birch, is tall and slender with pretty purple leaves. Cultivar 'Youngii', weeping birch, is a small tree which will grow to a height of 4 m (13 ft) if the trunk is supported by a sturdy stake. Its beautiful branches weep to the ground, making it a good lawn specimen. It grows well in cold areas.

B. populifolia, gray birch, zone 4, from North America, is similar to silver birch and grows to 10 m (33 ft). It has smooth, pale gray bark and long, narrow leaves.

Cultivation

Birches are generally adaptable to a wide range of conditions, although they prefer light soil and an open situation. Most varieties will thrive provided they have abundant summer moisture. Birches benefit from mulching to keep their roots cool. The species can be grown from seed collected in late summer and stored in the refrigerator until early spring. Sow seed on a moist soil and lightly cover. Cultivars must be budded or grafted onto seedling trees. Birches are prone to aphids and, in the Pacific Northwest, some species are attacked by bronze birch borer.

Climate

There are species to suit various climatic zones.