Eurasian aspen

Appearance

It is a substantial deciduous tree growing to 40 m tall by 10 m broad, with a trunk attaining over 1 m in diameter. The bark is pale greenish-grey and smooth on young trees with dark grey diamond-shaped lenticels, becoming dark grey and fissured on older trees.

The adult leaves, produced on branches of mature trees, are nearly round, slightly wider than long, 2–8 cm diameter, with a coarsely toothed margin and a laterally flattened petiole 4–8 cm long. The flat petiole allows them to tremble in even slight breezes, and is the source of its scientific name, as well as one of its vernacular names "langues de femmes" attributed to Gerard's 17th-century ''Herball''. The leaves on seedlings and fast-growing stems of suckers are of a different shape, heart-shaped to nearly triangular. They are also often much larger, up to 20 cm long; their petiole is also less flattened.

The flowers are wind-pollinated catkins produced in early spring before the new leaves appear; they are dioecious, with male and female catkins on different trees. The male catkins are patterned green and brown, 5–10 cm long when shedding pollen; the female catkins are green, 2–6 cm long at pollination, maturing in early summer to bear 10–20 capsules each containing numerous tiny seeds embedded in downy fluff. The fluff assists wind dispersal of the seeds when the capsules split open at maturity.

It can be distinguished from the closely related North American ''Populus tremuloides'' by the leaves being more coarsely toothed.

Like other aspens, it spreads extensively by suckers , which may be produced up to 40 m from the parent tree, forming extensive clonal colonies.

Habitat

Eurasian aspen is a water and light demanding species that is able to vigorously colonize an open area after fire, clear cutting or other kind of damages. After an individual has been damaged or destroyed, root suckers are produced abundantly on the shallow lateral roots. Fast growth continues until the age of about 20 years when crown competition increases. After that, growth speed decreases and culminates at about 30 years of age. Aspen can reach an age of 200 years.

It is a very hardy species and tolerates long, cold winters and short summers.

Aspen is resistant to browsing pressure by fallow deer due to its unpleasant taste.

This species is important for the hornet moth, which uses it as a host during the larval stage.

Evolution

Fossils of ''Populus tremula'' have been described from the fossil flora of Kızılcahamam district in Turkey which is of early Pliocene age.