Identifying aspen and cottonwood

Aspen

• Rounded or heart-shaped leaves with fine teeth, on stalks that are flattened sideways, so the leaves tremble in light air.
• Smooth, pale greenish-white bark with dark scars.
• Leaves turn yellow in autumn, often brilliantly gold.

Quaking aspen

Quaking aspen (Populus tremuloides) is the most widely distributed tree in North America. It grows in stands that are often clones, connected by roots, which send up new shoots after fire or logging. One famous aspen clone in Utah, called Pando, covers more than 100 acres.

Cottonwood

Eastern cottonwood (Populus deltoides) has large, triangular leaves with coarse teeth, also on flattened stalks. It grows beside rivers and has deeply ridged bark when old. In early summer female trees release cottony seeds that drift like snow.

Look-alikes

Birch leaves are similar, but double-toothed and pointed. Basswood and redbud have heart-shaped leaves, but they do not tremble.

In Britain

The European aspen (Populus tremula) is a native British tree of the Scottish Highlands, with rounded, toothed, trembling leaves. The Woodland Trust has a guide.

Trees in this group

• Quaking aspenPopulus tremuloides
• Eastern cottonwoodPopulus deltoides