Eucalyptus Smithii. Origin: Australia Eucalyptus smithii, or gully gum, is a native tree of northern Victoria and southern New South Wales, Australia. It naturally occurs on the lower slopes, gullies, and swamps, where soil does not dry out. Eucalyptus smithii essential oil is a woody, camphorous yet fresh essential oil that is particularly good for the respiratory system. It is the mildest of all the Eucalyptus and is suitable for use with children and the elderly.