Sometimes variegated trees and shrubs will have a branch (or more) come out green instead of the variegated pattern. Why does this happen?
Variegation causes more than one shade to appear in the plant on the leaves and stems. Some variegations are a type of mutation in plants called a chimera. They have less chlorophyll than non-variegated plants. This can cause them to live for a shorter time since the tree isn't able to make its food as efficiently.
Just as the original plant was able to mutate to a variegated state, branches may sometimes mutate to a "normal" state. They may be attempting to overcome the lack of chlorophyll in the other leaves.
Getting a Tree Back to Its Variegated State
The easiest way to return your tree or shrub to being purely variegated is to prune away the affected parts. The pruning tool you should use will depend on how high and thick your tree or shrub is. A good pair of pruners will work for many shrubs, but you may need a pruning saw for your trees.