There is a bit of a range overlap of American plum (Prunus americana) and Chickasaw plum (Prunus angustifolia). American plum has more of a northern range and Chickasaw plum more of a souther range.Angustifolia, the species name for Chickasaw plum, means narrow-leaved which was one of the details we used to distinguish them! Additionally, the margins are typically more sharply serrated in American plum than Chickasaw plum.We get ripe Chickasaw plum fruit in May in Alabama, but I believe that Ame