Brilliant idea

I mean, this has it's own problems because trees can rot, get diseases, get knocked/chopped down, their roots can become a hazard, they can catch fire, etc etc etc. If an eternal marker is what you're hoping for, it probably won't work out quite as you expected
'
Nevertheless, I still really like the idea

no one will know where your grave is and someone will eventually probably cut it down and you will eventually be forgotten.

This is how you end up with haunted forests

Overpopulation of people... overpopulation of trees... trees become our new overlords... end of the world as we know it

Wouldn't that cause the tree's roots to be jammed together?

It'd be cool until the tree roots started fucking everything up.

You guys really need to understand how important trees are.... facepalm

Also traps the zombies underground

A different perspective...if you will:
https: // youtu.be /pWo2-LHwGMM