An excerpt from Keepers of the Dead —
“Does the World Tree truly support all the worlds or does it simply cross some?” the Hall Warden asked. “The Havamal seems to contradict itself on many occasions. Yggdrasil is said to have roots in Midgard, Jotunheim and Hel; and the gods gather under its boughs, thus it is most likely in Asgard … but does it connect with the other worlds?”
“I understand your dilemma, Hall Warden,” Garrick responded, searching for the right words. “I see the World Tree as an allusion to the unity of all things and the belief in a connection between all the planes of existence, as opposed to a belief that the physical world is all that there is, or that the prime material plane is somehow less than the various spiritual realms that we encounter.
Yggdrasil is seen as being rooted in Middle Earth, Jotunheim, and Hel to show that the Great Tree relies on both the mundane and the sacred to exist, but that our experiences with the Great Tree will forever be sullied by illusion. Unless we take on the struggle of self-sacrifice on the Tree, much as did the All Father when he hung upon the tree for nine days in exchange for the Runes and Ancient Wisdom.
No one knows from where the Tree rises because it is a representation of the Primal Soul. The grand multiverse is connected by the allegory of the World Tree to symbolize the spirit being entwined with the physical. We are nothing if we deny any facet of our being. It is body, mind, and spirit joined that makes us whole.”
“Thank you, Gothi… you have given me much to ponder.”