Populus tremuloides aka Quaking Aspen

Populus tremuloides, or quaking aspen, belongs to the willow family. This tree sheds its leaves each year. Its native range spans subarctic North America south to Mexico. It grows across much of Canada and the United States. It has the widest range of any North American tree. Garden trees reach 40–50 feet [12.2–15.2 metres] tall. Some sources give a broader range starting at 20 feet [6.1 metres]. Their crowns spread 20–30 feet [6.1–9.1 metres] wide. Young trees have a slim, cone-shaped crown. The crown rounds out as the tree ages.

Young bark is smooth, pale green, cream, or silvery white. Older bark grows darker and forms deep grooves. Slender twigs are reddish brown, with pointed, resinous buds. The dark green leaves range from egg-shaped to almost round. Fine teeth line their edges, and their surfaces lack hairs. Flat leaf stalks let the blades shake in light wind. In fall, the leaves turn shades of gold and yellow. The pale trunks and fall leaves give the tree landscape value.

Catkins open in March and April, before the leaves emerge. Male and female flowers grow on separate trees in most cases. Some clones bear flowers of both sexes. Male flowers have red stamens among silky hairs. Female catkins hang down and develop small green capsules. These fruits hold tiny seeds wrapped in cotton-like fluff. Wind carries the seeds away from the parent tree. Neither flowers nor fruit provide much of a garden display. The tree draws birds, butterflies, and small mammals. It also gives wildlife food and cover.

Quaking aspen grows fast but has a short life. It suits cold regions and USDA zones 1–6. Give it full sun and moist soil that drains well. Rich soil with plenty of humus supports its best growth. It can also grow in sand, clay, and rocky ground. Sources note that it tolerates soil that is wet at times. Heat, humid summers, and urban pollution cause problems. Roots send up shoots that can form large clonal groves. Keep it away from drains, septic tanks, sewers, and sidewalks. It can colonise bare ground and help other trees establish. People have also used its wood and bark.

This tree needs much upkeep and faces many health problems. Cankers, rust, leaf spots, mildew, and dieback can damage it. Disease may make leaves fall before their usual season. Caterpillars, borers, aphids, and scale insects also attack it. Summer stress can increase damage from borers and dieback. Recorded foods include inner bark, sap, and bitter catkins. People have ground dried inner bark into flour. The bark also has a history of medicinal use. Its salicylates can cause heartburn or ringing in the ears. The cited hazard guidance warns against use by people with ulcers.