Reversion is the name given when a cultivar known for a particular leaf shape, colour, or other striking characteristic ‘reverts’ back to a different form found in the plant’s parentage. The term is often used to describe a variegated shrub or tree that produces non-variegated shoots.
During the growing season you can instantly recognise reverted shoots as pure green growths emerging from among the branches of a variegated plant. As these shoots contain more chlorophyll than variegated ones, they are more vigorous and can eventually take over the plant.
This is mainly a problem with variegated trees and shrubs, but can also affect coloured Phormium hybrids, with plants starting to grow pure green leaves. Also variegated plants such as hollies can produce all white or pale yellow shoots, but these are very weak and do not take over in the way that green ones do.
Variegated plants are generally selected from a sport, or mutation, of a pure green plant. The variegated part is then propagated by cuttings, grafting or division to retain its features. However, the mutations within these plants are not always stable and can be prone to ‘reverting’ back to pure green shoots.
Virus infections can cause a form of variegation. Very few variegated plants can be raised from seed as reversion is usually a growth disorder and not a genetic one.
Shoots that have reverted are much more vigorous than the variegated plant and should be pruned out completely or cut back into wood containing variegated foliage.