Not something you see every day, though I know it happens and have been told about alders growing out of hawthorns in a similar manner to this. Really cool, to be honest. The (epiphytic?) birch (Betula pendula) featured in the below images is, every few years, pruned back, so that its chances of surviving in the oak are better. However, as you’ll see below, one wayward root has done something very awesome!
A birch peering out from behind an oak stem, right…?Wrong! It’s growing in the oak stem.Here we can see its rooting system, reaching down to where nutrients and moisture are available.And one root has gone in search of the ground, it seems. And it has made it. If this birch survives and this oak stem fully decays, perhaps it’ll end up on ‘stilts’?Here’s a look at the oak stem, and we can see the root tracking down to the ground from underneath the bark (which has fallen off in places).
Arboriculture 