Eucalyptus trees are colloquially called gum trees in their native Australia, and the nickname has spread to other parts of the world. Other trees include the name "gum," even though they are not Eucalyptus trees.
Eucalyptus trees that produce sap are the ones most readily called gum trees. The nickname describes the scented sap that oozes down the trunk and hardens into gummy clumps.
Not all trees that incorporate the name "gum" are Eucalyptus trees. Some tree varieties, such as the Sweetgum and Black gum, belong to other families and are called gum trees for different reasons. For instance, the Sweetgum earned its name from American pioneers who used to scrape material from the tree to make chewing gum, according to the University of Florida.
An easy way to tell the difference between a true Eucalyptus and another type of gum tree is by studying the leaves. Eucalyptus trees tend to have long, thin leaves and produce a strong aroma. In Australia, koalas and termites are commonly found along their trunks and branches.