Cottonwood

Cottonwood — The cottonwoods are three species of poplars in the section Aegiros of the genus Populus, native to North America, Europe and western Asia.

The name is also commonly used for any species of poplar in the United States, including some poplars not in the section Aegiros, notably the Swamp cottonwood Populus heterophylla (in the section Leucoides) and the Black and Narrowleaf Cottonwoods P. trichocarpa and P. angustifolia (balsam poplars in the section Tacamahaca).

Those in section Aegiros are large deciduous trees 20-45 m tall, distinguished by thick, deeply fissured bark, and triangular-based to diamond-shaped leaves, green on both sides (without the whitish wax on the undersides of balsam poplar leaves), and without any obvious balsam scent in spring. An important feature of the leaves is the petiole which is flattened sideways, so that the leaves have a particular type of movement in the wind. The aspens (Populus section Populus) share this characteristic, but not the balsam poplars.

Male and female flowers are in separate catkins, appearing before the leaves in spring. The seeds are borne on cottony structures which allow them to be blown long distances in the air before settling to ground.

The cottonwoods are exceptionally tolerant of flooding, erosion and flood deposits filling around the trunk.

In the past up to five or six species were accepted, but recent trends have been to accept just three species.

Cottonwoods are widely grown for timber production along wet river banks, where their exceptional growth rate provides a large crop of wood within just 10-30 years. The wood is coarse and of fairly low value, used for pallet boxes, shipping crates and similar, where a coarse but cheap and strong wood is suitable. They are also widely grown as screens and shelterbelts. Many of the cottonwoods grown commercially are the hybrid between Eastern Cottonwood and Black Poplar, Populus × canadensis (Hybrid Black Poplar or Carolina Poplar).