The Rainbow Eucalyptus, also known as Mindanao Gum (eucalyptus deglupta) is often planted as an ornamental tree in tropical regions for its beautiful bark (it can be grown in zones 9 and 10). Native to Papua New Guinea, but naturalized throughout much of the South Pacific, they are fast growers, adding as much as 6 feet a year until they reach as high as 220 feet. They grow in full sun to partial shade, but they need a lot of water and grow best in a rain-forest environment.