Solitary Trees

I am like a tree. I have roots (past). I have a trunk (present). I have leaves (future).
Which tree am I?
Am I the skinny and smooth tree?
Am I the big, thick, and rough tree?
Am I the the tree covered with dog urine?
Am I the tree with my roots exposed?
Am I the tree with names carved into my trunk?   
There are so many different trees.
But they have one thing in common.
These trees stand in solitary.
They grow strong like me.