Yesterday, May 6th, was the fourth anniversary of the US release of Thor from Marvel Studios. This image of Yggdrasil is taken from that film.
Yggdrasil means literally “the terrible’s horse”, but may also mean “Odin’s gallows”, a story we will save for another day. Yggdrasil is the great world tree on which all the nine realms* in the Norse cosmos are supported. It is a great ash tree whose roots sink deeply into the darkness of Hel, where the dragon Nidhogg gnaws at its roots. Its top-most branches reach far above the glorious halls of Asgard, and an unnamed eagle rests at the very top of the tree. The squirrel Ratatosk is tasked with carrying messages between the eagle and Niddhogg. The three roots of Yggdrasil reach into important wells in Midgard, Jotunheim, and Hel.
Trees were sacred to many Northern/Germanic cultures, and we are aware of specific sacred trees for the Saxon people and at the temple at Uppsala (in what is now Sweden). Warden trees that protected and brought luck were a common practice that continued into the 19th century.
As in the picture above, Yggdrasil is understood somewhat differently for the alien Asgardians of the Marvel Cinematic Universe. They use the world tree as a metaphor to explain the cosmic connection between the nine different planets that made up the key planets in the cosmos as they understood it. Thor sketched this out to Jane on a notepad in the first Thor movie, and the connection became much more tangible in Thor: The Dark World when a “Convergence” made passage between these nine realms as easy as walking through a portal.
* Asgard, home of the Aesir, the gods with whom you are most familiar; Vanaheim, home of the Vanir, also gods; Alfheim, residence of the light elves; Midgard, where you now reside; Muspelheim, realm of fire; Svartalfheim, where the dark elves live; Jotunheim, land of the giants; Niflheim, the frozen lands of mist and ice; and Hel, the land of the dead.