The aspen is a native deciduous tree with a slender trunk and loose crown belonging to the willow family. It is widely distributed in Europe, Siberia, North Africa, and Anatolia.
The leaves of aspens are round to heart-shaped and tremble at the slightest breeze - hence the latin species name "tremula," meaning trembling. This trembling is attributed to the special structure of the long leaf stalk, which is flattened orthogonal to the leaf blade.
The aspen thrives on dry, nutrient-poor plots in sunny environments such as clearings, industrial fallow land, along railway tracks, and after forest fires, where it often appears as a pioneer species and forms larger groups due to extensive root sprouting.
The propensity of the American trembling aspen (Populus tremuloides) to form clonal colonies led to the formation of the oldest and heaviest known living organism on Earth, the Pando (from Latin "pandere," meaning to spread), in the Fishlake National Forest in Utah, USA. The entire clonal colony (genet) covers an area of 43.6 hectares, counts about 47’000 stems, and is estimated to be 14’000 years old. The stems are connected via rhizomes, forming a single large organism. While some stems die off and new ones appear, the colony as a whole persists.