Populus sect. Aigeiros — cottonwoods

Characteristics

Cottonwoods are typically large, deciduous trees with broad, deltoid (triangular) leaves that flutter on flattened petioles. The bark is often furrowed on older trees. In spring they produce catkins that develop many small seeds attached to tufts of silky hairs, aiding wind dispersal. Wood is relatively light and soft compared with slow-grown hardwoods.

Species and distribution

• Populus deltoides — eastern or plains cottonwood, widespread in North America.
• Populus fremontii — Fremont cottonwood, western North America (closely related or sometimes treated as a subspecies).
• Populus nigra — black poplar or European cottonwood, native to Europe and parts of western Asia.

Uses, ecology and importance

Cottonwoods are prominent riparian trees: they stabilize stream banks, provide shade and furnish habitat and food for birds and mammals. Their rapid growth makes them useful for windbreaks, reclamation and short-rotation wood production (pulp, biomass and light construction). The profuse cotton-like seed hairs can be a seasonal nuisance in urban areas but are a natural dispersal mechanism.

Cultivation, hybrids and challenges

Many hybrids between cottonwood species and cultivars have been developed for forestry and landscaping to combine vigor with disease resistance. Downsides include brittle wood, propensity to drop large branches in storms, invasive surface roots and vulnerability to pests and fungal diseases such as canker and leaf rust. Proper siting and pruning reduce some risks.