black gum, ornamental deciduous tree (Nyssa sylvatica family Nyssaceae) native to E North America. The leaves turn bright scarlet in the fall. The very tough wood was used for wheel hubs and other purposes. It is sometimes called sour gum, tupelo, and pepperidge, names also given other species of the genus, some native to Asia. This is the source of the popular tupelo honey. The genus Nyssa is probably derived from an ancestral dogwood and is included by some botanists in the family Cornaceae (dogwood family) of the division Magnoliophyta, class Magnoliopsida, order Cornales.