Black cottonwood is recognized by the deep, roughly furrowed gray bark on mature trees. The large, broad ovate leaf is characteristic of the poplar family. Many tribes ate the sweet inner bark in the spring, when the sap was running. After the thick outer bark had been removed, the inner bark (cambium) could be scraped off. The wood was said to be ideal for tipi fires, because it did not crackle and produced clean smoke.