About 90% of a Eucalyptus tree s roots grow in the top 300 - 400 mm of soil, which makes perfect sense when you consider where they come from: a challenging environment, where the ability to be the first to access limited rainfall is vital for survival.osition your Eucalyptus at least two thirds its potential mature height away from a building on ordinary loamy garden soils and an even greater distance away from buildings if you have a clay soil (which has a tendency to shrink in periods of drought).