Populus sect. Aigeiros

Populus section Aigeiros is a section of three species in the genus Populus, the poplars. Like some other species in the genus Populus, they are commonly known as cottonwoods. The species are native to North America, Europe, and western Asia. In the past, as many as six species were recognized, but recent trends have been to accept just three species, treating the others as subspecies of P. deltoides. They are large, deciduous trees that are 15–30 m (50–100 ft) tall and diameters of 4 m (13 ft), distinguished by thick, deeply fissured bark and triangular-based to diamond-shaped leaves that are green on both sides (without the whitish wax on the undersides) 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. Male and female flowers are in separate catkins, appearing before the leaves in spring. The seeds are borne on cottony structures that 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. Although each of the three cottonwood species has a different leaf pattern, they all have the same general diamond leaf shape.