What does it mean to be a tree? Undead stumps and albino redwoods.
This is a fascinating article about how some stumps are stay alive by grafting their roots to other trees. In exchange for the energy derived from other trees, they provide water siphoned up at night when the other trees aren’t active. It’s not clear if the grafting happened before or after the tree was cut down.
There’s another example of this described in this article. Redwoods that can’t photosynthesize their own nutrients, but get their nutrients from other trees, and in return seem to help process toxins.