Juvenile and adult foliage

Perhaps it is not fully understood that there is a substantial difference between the juvenile, intermediate and adult foliage in some of the Eucalypts e.g. E. perriniana or E. gunnii. After 2 to 3 years the tree will stop making juvenile foliage altogether. If you require only the juvenile foliage e.g. for cut foliage the only way is to cut back as described to a single stump at the end of March after at least two full seasons growth. The young buds will break from the base after 4 to 6 weeks. See the notes on coppicing. It is not successful to just cut the top off as this causes the tree to produce more adult foliage. A signal has to be sent to the tree that it has been severely damaged and it will then go through its succession of leaf production again starting with the required juvenile foliage.

Why do the leaves change shape at different stages of maturity? It has been suggested that the juvenile leaf is the ancestral form and in passing from the juvenile to the mature stage the plant is repeating the historical evolutionary development of the species which would have taken place as the continent of Australia separated from the Antarctic and South America and moved towards the tropics over a period of many millions of years.

As all Eucalyptus trees are evergreen to accommodate the increase in stem girth some of the older leaves and small branches are shed during the growing season. In young plants and trees this is quite noticeable whilst the tree is actively growing. Depending on species the leaves turn brown, yellow, spotted, pink or red before falling.