He is man-shaped and as much bigger than an Ogier as an Ogier is bigger than a man. He appears to be made of woven leaves and vines. He hair is grass, his eyes are hazelnuts and his fingernails are acorns. There is a deep scar running up his head. (TEotW,Ch48)
Chronology
Someshta dances as Coumin participates in his first singing. (TSR,Ch26)
The Green Man takes Moiraine and the others to a cave where the Eye of the World is located. When Aginor and Balthamel arrive he commands them to leave. Balthamel burns him, but he grabs Balthamel, rotting him. As he dies, he grasps an acorn, which grows into a mighty oak. (TEotW,Ch50)
Other References
TEotW,Ch4 - Thom offers to tell stories of the Green Man.
Books 