I have always assumed that the "green man" represented the force or spirit of nature. Perhaps the leaved figure is in fact a representation of that force?
I first encountered a reference in the song, "Gartan mothers lullaby"

Where the "green man's thorn" (gorse or whin), "is wreathed in rings of fog"
There are other references to various Pagan spirits in the song.

I live in an area where in the very early morning the misty wreaths do walk among the whins all of which are decorated by cobwebs glistening with condensation......Ake