Family: Salicaceae
Common Name: Poplar

The 35 species of these widely grown deciduous trees are found throughout the northern hemisphere. In the UK, they are mainly grown in rural areas and large gardens as windbreaks and tall screens. They are also excellent for avenue plantings. The broad, alternate leaves come in various tonings and the pendulous, catkin flowers appear in spring while the tree is still bare. Colour in autumn is usually golden.

Species

P. alba, white or silver poplar, zone 3, is a beautiful tree from Europe, North Africa and central Asia, growing over 20 m (65 ft) high. It has broadly oval, dark green leaves, covered in white or gray down on the under-sides. The leaves turn a rich gold in autumn. This species can tolerate low-level drought, salt-laden winds and poor alkaline soils. The form pyramidalis has an erect, columnar habit, growing to 30 m (100 ft) or more when fully mature.

P. balsamifera, balsam poplar, zone 2, from North America, grows up to 30 m (100 ft) and has glossy, almost yellow branches and oval, shiny leaves, which are white on the reverse side.

P. x canadensis, zone 4, is very upright, with rounded, triangularshaped leaves. It grows over 20 m (65 ft) and the trunk has heavily furrowed bark.

P. deltoides, cotton-wood, zone 2, from eastern North America, grows up to 30 m (100 ft) and spreads to about half the height. It makes a lovely shade tree for rural properties, but is relatively short lived and very brittle in high winds. The very large, almost triangular, glossy, green leaves are veined with yellow.

P. nigra, black poplar, zone 2, from Europe and central Asia, grows 15-30 m (50-100 ft), with a broad head of foliage. The diamond-shaped leaves are bronze when young, changing to a bright green as they mature. In autumn, they turn a pale yellow before falling. This species is best known by one of its cultivars, 'Italica', or Lombardy poplar, which grows in the shape of a spire and has narrower, heart-shaped leaves. This poplar is quite widely planted in rural areas for its use as a windbreak.

P. tremula, aspen, zone 2, from Europe, Asia and northern Africa, grows to about 25 m (80 ft), with a dark gray, fissured bark. The fine, rounded leaves are borne on very fine branch-lets, so they rustle in the lightest breeze. They are coloured bronze-red when young, deep green when mature. In autumn, they colour yellow.

P. tremuloides, the quaking or American aspen, which grows to 15-20 m (50 65 it), has similar leaves to P. tremula and they too rustle in the slightest breeze.

P. yunnanensis, zone 5, is a broad-growing tree with leaves bright green above and grayish green beneath. The leaf stalk and mid-vein is red. Growing to around 20 m (65 ft), the yunnan poplar is useful for shade. It does better than many other species of poplarin warm districts with lower rainfall.

Cultivation

All poplars grow quickly and easily, preferring cool temperate climates with regular rainfall. Plant in deep, moist, well-drained fertile soil in full sun. All need ample water in the growing season. Most poplars are extremely vigorous and they should be planted where there is ample room for their enormous root systems-at least 18 m (60 ft) away from drains and paths. Propagate from 30 cm (12 in) long hardwood cuttings in early winter. Those that tend to sucker very freely, particularly the silver-leaved types, may be grafted on non-suckering rootstock. All species will transplant easily at any size. No pruning is necessary. Poplar rust damages a great many species and cultivars. Control is impossible on large trees. For new plantings, seek out varieties which have resistance to rust.

Climate

There are species suited to various climatic zones. All are very hardy.