There are over 500 different species of Eucalyptus, some are hardy, and some are not. Most have bluish foliage. They are all tall trees, some growing up to 25 metres tall. For the best foliage effect, it is best to keep the tree pruned right back, so that the new growth will produce juvenile foliage, as in the picture, which is bluer and rounder than the mature foliage of larger trees. Many Eucalyptus trees shed their bark, which, when dried, produces very useful slivers of bark, reminiscent of cinnamon bark, to use in arrangements. I have Eucalyptus gunnii in my garden, which is one of the hardiest species. Eucalyptus niphophila is a bit more tender, but has brighter foliage.