Greenies

 

Interesting stuff about The Green Man.

From Wiki:-

"Green Man" type foliate heads first appeared in England during the early 12th century deriving from those of France, and were especially popular in the Gothic architecture of the 13th to 15th centuries. The idea that the Green Man motif represents a pagan mythological figure, as proposed by Lady Raglan in 1939, despite its popularity with the lay public, is not supported by evidence

So not as ancient as you may think! Eh? 

Correctly known as foliate heads, then

Usually referred to in art history as foliate heads or foliate masks, representations of the Green Man take many forms, but most just show a "mask" or frontal depiction of a face, which in architecture is usually in relief. 

In terms of formalism, art historians see a connection with the masks in Iron Age Celtic art, where faces emerge from stylized vegetal ornament in the "Plastic style" metalwork of La Tène art. Since there are so few survivals, and almost none in wood, the lack of a continuous series of examples is not a fatal objection to such a continuity.

The Oxford Dictionary of English Folklore suggests that they ultimately have their origins in late Roman art from leaf masks used to represent gods and mythological figures. A character superficially similar to the Green Man, in the form of a partly foliate mask surrounded by Bacchic figures, appears at the centre of the 4th-century silver salver in the Mildenhall Treasure, found at a Roman villa site in Suffolk, England; the mask is generally agreed to represent Neptune or Oceanus and the foliation is of seaweed.

Thats enough heads for now. If you want to know more, see the wiki link above.