Nyssa aquatica, commonly called the water tupelo, cottongum, wild olive, large tupelo, sourgum, tupelo-gum, or water-gum, is a large, long-lived tree in the tupelo genus (Nyssa) that grows in swamps and floodplains in the Southeastern United States.Nyssa aquatica trunks have a swollen base that tapers up to a long, clear bole, and its root system is periodically under water. Water tupelo trees often occurs in pure stands.