The concept of the Tree of Life crosses many cultures and religions. Generally it connects Heaven and Earth, or the Natural World to the Underworld. Northern Europe in ancient times was heavily forested and it's quite natural for people to relate their lifes to trees.
In Norse and Old Germanic mythology there is the Yggdrasil tree, a massive tree possibly an ash connecting the Nine Worlds.
Trees are often the central point of feasts and rituals. In the British Isles the mighty oak and yew tree are reverred particularly as they survive for centuries with their roots being as large as the tree over ground.