Actually, in Chineese medicine, when one learns the basics of the elements etc, there are some things that relate to trees.
the 'Wood' is one of the elements, green is the color connected to it (strange, isn't it?!) and the feeling connected is anger. It is said that when a person is angry, he should hug a tree. I guess it should bring calmness (just don't hug the thorny ones...
But the other thing I wanted to write is about books relating to trees in nice ideas-
The first is 'The giving tree' by Shel Silverstein, which is a beautiful book.
the other touches many subjects but has a small part to do with plants and it is 'The book of pages' by David Whiteland (I think).
All in all, these are nice books about life and what we make of it.
So, enjoy your hug