The aspen is an easy tree to recognise in Finland from the round leaves. The leaf stalk is long and flattened so that even the gentlest breeze produces the typical fluttering in both movement and sound. In young trees the bark is a smooth grey, which makes the species stand out when seen from a distance; later they become vertically furrowed. From close up, the trunks can often be seen to be decorated by splashes of a yellow lichen (Xanthoria parietina), called variously common orange lichen, yellow scale, maritime sunburst lichen and shore lichen, among others.
The 10 cm pods of the female catkins open to release tufts of white seed cotton, which are spread far and wide by the wind. The seeds contain no reserve nutrition so very few of them germinate to grow into seedlings and later new trees. Mainly the species spreads by means of roots suckers. The clones arising from a particular parent do not mix with those from another tree and quite often in autumn clone groups can be distinguished as patches of slightly different colour, some reddish, others more yellow, indicating the borderlines between the clones.
The aspen seldom exceeds 100 years in age. The hollow trunks age attractively and support a wide range of mosses and lichens, not to mention a varied fauna, as they slowly rot and become, finally, humus.