Gum trees (eucalyptus) grow colorful bark patterns on the Overland Track. Cradle Mountain-Lake Saint Clair National Park, Tasmania, Australia. Mostly native to Australia where they dominate the tree flora, Eucalyptus is a diverse genus of flowering trees (and a few shrubs) in the myrtle family, Myrtaceae. Many are known as gum trees because of copious sap exuded from any break in the bark. Published in Light Travel: Photography on the Go book by Tom Dempsey 2009, 2010.