Several native species and varieties of poplar are known collectively as cottonwood. Not many are actually planted. They just have a sneaky way of appearing in well watered parts of the garden that are as damp as the riparian areas that they naturally inhabit. Only Fremont cottonwood, Populus fremontii, gets planted, rarely, and only in big spaces that can accommodate its grand scale.
Although too big and too thirsty for most refined landscapes, cottonwoods work well for shade or erosion control in big parks. However, they need to be in a lawn or irrigated landscape if they are not close enough to riparian areas to disperse their roots into soil that is somewhat moist through most of the year. Even in riparian situations, young trees need irrigation until their roots disperse.
Cottonwoods grow fast and big, with aggressive and potentially destructive roots. They should not be planted too close to pavement or septic systems. Vigorous trees might sometimes need to be pruned to reduce excessive weight. Big trees might grow to nearly a hundred feet tall, with wide canopies. Bark is handsomely furrowed with age. The deciduous foliage turns yellow in autumn.