The Differences Between Aspen and Cottonwood

Size and Habit

• Cottonwood trees are large trees; the eastern cottonwood tree may reach 80 to 100 feet, and the black cottonwood tree can grow to a height of 200 feet. Aspens are smaller trees and have a suckering or spreading habit, where new trees sprout from the roots. Quaking aspens can reach 40 to 50 feet, while bigtooth aspen grows up to 50 or 70 feet tall.

Leaf Size and Shape

• The leaves of cottonwood trees are larger than those of aspens. Eastern Cottonwood and black cottonwood trees have triangular shaped leaves, ranging in size from 2 to 5 inches and sometimes up to 8 inches for eastern cottonwood, and 3 to 6 inches for black cottonwood trees. The leaves of quaking aspens are much smaller, 1.5 to 3 inches, and are more rounded than cottonwood leaves. Quaking aspen leaf stems are flat, thin and as long as the leaf blades themselves, causing leaves to tremble in the slightest breeze. Bigtooth aspen leaves are somewhat larger, 3 to 4 inches, and are rounded or slightly oval.

Leaf Margin and Underside

• The margins of cottonwood leaves have rounded teeth, while quaking aspen leaves have finely serrated leaf margins. Bigleaf aspen leaf margins are distinguished by coarse, pointed teeth. Eastern cottonwood leaves are medium green on top and covered with white hairs on the underside, while black cottonwood leaves are hairless underneath and have rusty markings. Aspens have dark green leaves with smooth, light-colored undersides.

Stems and Fruits

• The stems or twigs of cottonwood trees are grayish-yellow, while quaking aspen and bigtooth aspen have reddish-brown stems. Cottonwood female trees bear encapsulated seeds, 0.25- to 0.33-inch long capsules, which open up to produce white cottony balls. In urban settings, the cottony tufts falling on the ground are sometimes considered messy. Aspen trees bear similar but smaller, insignificant seed capsules.

Bark

• Cottonwoods have greenish-brown or grayish-brown bark. The bark is smooth when the trees are young, but becomes highly ridged as trees mature. Aspens have smooth, light, greenish-gray bark. Some quaking aspens have nearly white bark. As aspen trees get older, the bark may darken and show some furrows, mainly on the bottom of the trunks.