Cottonwoods, in the Poplar genus (populus), are fast-growing riparian trees which grow in the western United States. These are the tall, large-leaved trees you see in the desert, whenever there's water. Sometimes during droughts they will die back to little globs of leaf on each stem and are very picturesque. Cottonwoods can grow extremely fast, some up to 20 feet in a year! Also their roots grow extremely fast and can be damaging to structures. They dont really make a good tree for a suburb but are beautiful in parks or wide open areas, and can be full sized trees in about 20 years. They propagate mainly by broken branches lodged in floodplains... they often need floods to reproduce. sometimes after a flood hits an area the whole affected area will be covered by young cottonwoods in a few months.