The Green Man has been found in many cultures from many different ages around the world. The Green Man is usually related to natural vegetative deities. He is primarily interpreted as a symbol of the Earth, and of rebirth, representing the cycle of growth each Spring.
The Green Man is said to have developed independently in the traditions of separate ancient cultures, and is found throughout history from the ancient Egyptian Osiris to Norse mythology, modern Paganism and esoteric Sufism.
In Wicca, the Green Man has often been used as a representation of the Horned God, who has aspects of the Celtic Cernunnos and the Greek Pan. (Also check out The Oak King and The Holly King)