Aspens belong to the same genus as poplars and cottonwoods, a genus distinguished by their triangle-shaped, toothed leaves. They grow quickly and don't live long, but the roots of seemingly dead trees constantly give rise to new trees through root suckering. Botanists have discovered aspen groves growing from rootstock exceeding 10,000 years of age, according to George A. Petrides, author of the field guide "Eastern Trees." Aspens occur throughout the world.
One of the best-known aspen trees, the quaking aspen (Populus tremuloides) earned its name for the tendency of its foliage to flutter and tremble in the lightest of breezes. Unlike most of its relatives, the quaking aspen's leaves have a nearly round rather than pointed shape, edged with the single teeth common to the Populus genus. A native on both U.S. coasts, the quaking aspen can tolerate extreme colds and grows into northern Canada. The dark green summer foliage changes to yellow in the fall, but despite the attractive color, the quaking aspen presents numerous problems as a landscape tree, according to the University of Connecticut horticulture department, where it presents a hazard to sidewalks and sewers, sends up frequent root suckers and only lives briefly.
The bigtooth aspen (Populus grandidentata) grows in a more limited range than the quaking aspen, occurring primarily in the northeastern and north-central United States and southeastern Canada. As the name suggests, the teeth typically found on the leaves of the Populus genus are especially large on the bigtooth aspen. According to the U.S. Forest Service, the bigtooth aspen prefers sandy soils and floodplains, and after removing trees from an area of the forest, the bigtooth aspen is one of the first to return to colonize the area, with as many as 60,000 root suckers emerging per hectare after a forest fire. Bigtooth aspen grows primarily with other aspens and poplars, and its foliage, twigs and buds feed local wildlife.
The European aspen (Populus tremula) is one of the world's most widely distributed trees, ranging from the Arctic to northern Africa and stretching from western Europe to Japan, according to the Trees for Life project. Like quaking aspen, the leaves of European aspen have a rounded shape with wavy margins, and the leaves flutter in the breeze. Leaves emerge coppery-brown in the spring, change green and become yellow or red before dropping from the tree in the autumn. Like other aspens, the European aspen reproduces vigorously through root suckering, quickly arising in areas deforested by logging or fire. Deer and beavers feed on the aspen, and the tree provides a source of shelter for woodpeckers.