OK, I have read:

The name of the Green Man
by Brandon S. Centerwall

and he seems to argue that their is enough evidence to connect the foliate heads with the Green Man of plays and pageants. I do not have the academic background to judge how sound this conclusion is.

Since their are so many foliate heads in churches it is tempting to conclude that some foliate heads are bound, by chance, to look like something or other.

If the foliate heads came out of the churches and into the plays what does it suggest? Anything or nothing?