Any tree of the genus Populus, family Salicaceae, marked by simple, alternate leaves that are usually broader than those of the willow, the other American representative of this family. Poplars have scaly buds, bitter bark, flowers and fruit in catkins, and a five-angled pith. The Janka hardness for poplar is 432 lb-force (196 kg-force); its density is 29 lb/ft³ (465 kg/m³).