What Is Yggdrasil, the World Tree?

Yggdrasil connects nine worlds, though the sources do not agree perfectly on the list. They include Asgard, home of the gods, Midgard, the world of humans, Jotunheim, land of the giants, and Hel, the realm of many of the dead.

In Norse mythology the tree is not a decoration. It is the structure of reality. Gods travel between worlds along it, and the gathering place where they hold council sits beneath it.

Yggdrasil is crowded with life, and much of it is busy damaging the tree. An eagle sits at the top, a dragon called Nidhogg gnaws at a root, and four stags eat the branches.

A squirrel named Ratatoskr runs up and down carrying insults between the eagle and the dragon, which is one of the more entertaining details in Norse mythology. The tree is constantly being eaten, and constantly being tended by three figures who water it from a sacred well.

Three roots reach down to three wells, and each carries meaning:

• •The well of Urd, where the Norns decide fate
• •Mimir's well, a source of wisdom guarded closely
• •Hvergelmir, a spring from which many rivers flow

The name Yggdrasil is often read as the horse of Ygg, and Ygg is a name for Odin. That connects the world tree to one of the strangest stories in Norse mythology, in which Odin hangs himself from the tree for nine nights, wounded by his own spear, to gain knowledge of the runes.

It is a sacrifice of himself to himself, and it fits the picture of Odin as a god who trades comfort and even body parts for wisdom. The tree is where that exchange happens.

Yggdrasil is the most famous world tree but not the only one. Similar images appear widely, including in Siberian shamanic traditions, in Mesoamerican cosmology and in aspects of Hindu and Persian material.

Scholars are careful about what this proves. A tree is an obvious way to picture a structure with roots below, a trunk in the middle and branches above, matching an underworld, a human world and a sky world. The similarity may reflect shared inheritance in some cases and independent invention in others, and separating the two is genuinely difficult.

Almost everything you read about Yggdrasil comes from a small set of Icelandic texts written down in the thirteenth century. Poems collected in the Poetic Edda, especially the one in which a seeress describes the creation and end of the world, mention the tree, its wells and its creatures. Another poem, spoken by Odin in disguise, lists many of the animals living on it. Snorri Sturluson's Prose Edda then organised this material into a more systematic account, and much of the tidy picture of nine worlds comes from his arrangement.

These authors were Christians writing more than two centuries after Iceland converted, so scholars read them carefully. Snorri was collecting and explaining old poetry, but he also filled gaps and sometimes seems to have smoothed over contradictions that the original tradition left open. There is outside evidence that sacred trees mattered in pre-Christian Scandinavia. The eleventh-century writer Adam of Bremen described an evergreen tree beside the temple at Uppsala in Sweden, and historians often link such real trees with the mythical one, though how directly is still discussed.

Yggdrasil plays a part in Ragnarok, the great final battle in which many gods die and the worlds are destroyed by fire and flood. In the poem of the seeress, one sign that the end has come is that the tree trembles and groans. It is a powerful image: the structure that held reality together shakes as the order of the cosmos collapses. The sources do not clearly say that the tree is destroyed, and that silence has led to different interpretations.

Both the poems and Snorri describe a new world rising green from the sea after the destruction, with some younger gods surviving. Two humans, named Lif and Lifthrasir, are said to shelter during the catastrophe in a place called Hoddmimir's wood, living on morning dew, and to repopulate the earth afterwards. Many scholars think this wood may be another name for Yggdrasil itself, since Mimir is linked with one of its roots. If so, the world tree not only frames the cosmos but also protects the seed of the next one.

The sources call Yggdrasil an ash, yet the seeress's poem also says it stands evergreen above Urd's well. Ash trees lose their leaves in winter, so the detail has puzzled readers. Some scholars suggest the tree was imagined as a yew, a tree that stays green all year and can live for many centuries. One proposed origin of the name even reads it as yew pillar rather than horse of Ygg. Others answer that a cosmic tree need not follow ordinary botany, since being green forever may simply mark it as beyond normal time and decay. The question remains open, and both readings have serious supporters.

Continental Germanic peoples seem to have had a related idea. Frankish annals record that in 772, during his wars against the Saxons, Charlemagne destroyed a sacred site called the Irminsul. A ninth-century monk described it as a large wooden trunk set upright in the open air, which the Saxons regarded as a universal column holding up everything. Nobody knows exactly what it looked like, and it was a pillar rather than a living tree. Still, the idea of one central support for the whole world, honoured at a real place, sits close to Yggdrasil and suggests the image was older and wider than Iceland.

Yggdrasil reached a huge modern audience through Richard Wagner's operatic cycle The Ring of the Nibelung, first performed complete in 1876. At the start of the final opera, Twilight of the Gods, three Norns spin the rope of fate and recall the world ash tree. They tell how the chief god, Wotan, drank from the spring beneath it, giving an eye as payment, and broke a branch from the tree to make his spear. The wounded tree slowly withered and the spring dried up. Later, Wotan had the tree felled and its logs stacked around Valhalla, ready to burn when the end comes.

Wagner combined Norse and German sources freely, and his version shows how the tree keeps being reworked. More recent comics, films and video games often present the nine worlds as separate planets or realms hanging from the branches, connected by bridges or portals that heroes travel along. That image owes a great deal to Snorri Sturluson's tidy thirteenth-century arrangement and very little to the older, messier poems, which never give a clear map. When you meet Yggdrasil in a modern story, it is worth asking which details come from the medieval sources and which were invented to make the cosmos easier to film or play.

Yggdrasil, the world tree, is the ash that binds the nine worlds of Norse mythology together, constantly damaged and constantly tended, which makes it a fitting image for a cosmos the Norse never saw as safe or permanent.