Fasciated Forsythias

All gardeners will, sooner or later, come across examples of fasciation. This is a condition where a stem becomes flattened - sometimes bizarrely so. A wide range of plants may be affected by this malformation with lilies and Forsythias particularly susceptible. 

Forsythia with fasciated stem from a
garden in Byfield. 19 May, 2013

I saw an example earlier today in a friend's garden and was glad to reassure her that the condition - a form of what are known as "disturbed growth phenomena" is harmless. The study of these abnormal growths is known as "teratology, and my old friend Sean Karley - the plant gall recorder for Northants - is of the opinion that these oddities should be mapped and recorded. He has a point.

The fasciation shown in my photograph is typical, with a flattened stem and fan-shaped leaf cluster. Sometimes a whole head of flowers may be affected, particularly among members of the Daisy Family, with remarkable consequences. By googling "fasciation" a range of these abnormalities may be viewed.

Various explanations for fasciation have been put forward with hormonal imbalance the most plausible suggestion but in fact a number of factors may be involved and research continues.