Alder is another of the many riparian hardwoods found throughout the northern hemisphere. They are of the genus Alnus and are charactarized by fairly big leaves and distinctive seed structures. These trees are commonly found in association with birch, cottonwood, and willow

Alders are among the most useful trees along streambanks and levees, as the hold the banks together very strongly and discourage erosion quite effectively. Their roots can be exposed to air or their trunks can be buried under feet of sediment, and they still will survive. They can also be submerged for long periods of time without dying. Very few trees can boast all of this