One of the most mind-blowing moments of my life came when a truth about trees was pointed out.
For all that we see above ground - the soaring branches and over-arching leaves - there is a mirror of it beneath our feet. The roots are equally broad and expansive.
They have to be, or else the tree would fall down through lack of foundation. Or die, because its anchors are not providing an adequate supply of nutrients to feed its towering bulk.
Call it metaphor or actuality, but this is a concept not lost on the religions of the world. Especially not Paganism, with its spiritual tenets so beautifully interlinked with the natural world.
The connection between what is seen, and what remains unseen, is a pervasive idea. We can touch the reality of this world, but the other becomes an article of faith. Its necessary presence is deduced, and may even be touched in spirit. (Or with a spade, if we're still going with an actual tree and its roots.) But its concealed nature mostly requires a measure of belief to discern.
The Tree of Life represents a union. Perhaps the most profound of all. It channels the same powerful energy through the Other World, this world and the Nether World. What touches one, touches all.
Or, as the Wiccans say, as above, so below.