Gum Tree, any tree that yields a sticky substance known as gum. The sour gum, also called tupelo, is common in the eastern United States. Other North American gum trees include the sweet gum and the eucalyptus, which was introduced into California from Australia. The sapodilla tree of southern Mexico and Central America is the source of a gum called chicle, which is used as the base for many types of chewing gum.