Populus heterophylla, also known as downy poplar, swamp poplar and swamp cottonwood, is a large deciduous poplar belonging to the Populus genus of the family Salicaceae. This species can grow on sites that have too much water for other native poplars. On the IUCN Red List this species is listed as "least concern".
Swamp poplar can reach a height 50 to 100 ft at maturity. The trunk and branches are a light to medium grey, with the trunk being coarsely furrowed. The leaves are alternate deciduous that are 4-6 inches long and 3-4 inches across. Mature leaves are medium to dark green on their upper surface and pale green on the lower surface. Petioles are 2-3 inches long and tend to be between pale green or pale yellow. This species is pollinated by wind. This species flowers in April and fruits May-June.