Aspen (tree)

Aspen (tree), common name for certain related trees (see Poplar), particularly the so-called quaking aspens, several species of which have the petioles, or leafstalks, so compressed that the leaves can move easily from side to side but not up or down. A breeze sets all leaves of one of these trees into motion. The most familiar species are the American aspen, found in North America; the large-toothed aspen, found in eastern Canada and the United States; and the European aspen, found in Europe, western Asia, and northern Africa.

Scientific classification: Aspens belong to the genus Populus, of the family Salicaceae. The American aspen is classified as Populus tremuloides, the large-toothed aspen as Populus grandidentata, and the European aspen as Populus tremula.