Trees have always been something more than just plants to the mankind. The worship of trees might be forgotten, but still the symbol of tree survives in our subconscious. Almost every nation has myths and legends about trees, placing the tree as the central axis of the world, or worshipping it as a dwelling place of gods or spirits, the giver of knowledge, connection between worlds or as ancestors of the tribe.
In Norse mythology, a giant ash tree - Yggdrasil - represents "axis mundi", around which the 9 worlds (the world of people - Middle-earth, being one of them) are organized. A giant snake, Níðhöggr, gnaws at its roots, but they always grow anew.
Yggdrasil Seed by ArdiRaYggdrasil by Prasa
The biblical Tree of Knowledge has even some similarities to Yggdrasil. The snake is present, also, an