White Poplar is a species of poplar, most closely related to the aspens. It is native from Spain and Morocco through central Europe (north to Germany and Poland) to central Asia. It grows in moist sites, often by watersides, in regions with hot summers and cold to mild winters.
It is a medium-sized deciduous tree, growing to heights of up to 16-27 m (rarely more), with a trunk up to 1 m diameter and a broad rounded crown. The bark is smooth and greenish-white to greyish-white with characteristic diamond-shaped dark marks on young trees, becoming blackish and fissured at the base of old trees. The young shoots are covered with whitish-grey down, including the small buds. The leaves are 4-15 cm long, five-lobed, with a thick covering of white scurfy down on both sides but thicker underneath; this layer wears off the upper side but not the lower, which stays white until autumn leaf fall. Larger, deeply lobed leaves are produced on fast-growing young trees, and smaller, less deeply lobed leaves on older, slow-growing trees. The flowers are catkins up to 8 cm long, produced in early spring; they are diocious, with male and female catkins on separate trees; the male catkins are grey with conspicuous dark red stamens, the female catkins are greyish-green. The female catkins lengthen to 8–10 cm after pollination, with several green seed capsules, maturing in late spring to early summer. It also propagates by means of root suckers growing from the lateral roots, often as far as 20-30 m from the trunk, to form extensive clonal colonies.
White Poplar hybridises with the closely related Common Aspen Populus tremula; the resulting hybrid, known as Grey Poplar, is intermediate between its parents, with a thin grey downy coating on the leaves, which are also much less deeply lobed than White Poplar leaves. It is a very vigorous tree with marked hybrid vigour, reaching 40 m tall and over 1.5 m trunk diameter (much larger than either of its parents). Most Grey Poplars in cultivation are male, but female clones are occasionally found.
It requires abundant light and ample moisture, and stands up well to flood water and slightly acidic soils. Its green-and-white leaves makes it an effective ornamental tree but the root suckers may cause problems in some situations. It is very attractive as an open-grown tree in water meadows, and, because of its extensive root system and tolerance of salt, is also planted to strengthen coastal sand dunes.
The majority of White Poplars in cultivation in northern Europe are female trees.
In intensive forest management it is being replaced by various cottonwood hybrids. The wood is soft, and used to make cellulose and for cheap boxes.