I'm finding trees quite hard to illustrate. I've always had an artistic streak in me and have had exhibitions in London, NY, Paris & Sydney, but illustration is a different matter. The problem with trees is that if you make them look too simple or abstract it makes the whole illustration look too simple (eg Pink Panther).
I've tried to compromise by drawing a number of different shaped and coloured leaves, then scatter them over a simple tree trunk and a few branches. A simple shadow is useful to add some depth.
Anyway, unless I make any last minute changes this is the tree that will appear in Tortoise George. It's worth the effort. After all, he does live in the woods.