The Green Man motif has many variations. Found in many cultures around the world, the Green Man is often related to natural vegetative deities springing up in different cultures throughout the ages. Primarily it is interpreted as a symbol of rebirth, or "renaissance", representing the cycle of growth each spring. Some speculate that the mythology of the Green Man developed independently in the traditions of separate ancient cultures and evolved into the wide variety of examples found throughout history. (From Wikipedia)
If you look closely, you will see the face of the Green Man in nature, especially now when the leaves are new.