PaintFX
booooo hiss no!!! 
Stand up slowly from your computer (taking time to adjust to the lack of a mouse/keyboard).
Slowly walk towards the door. Open said door.
Walk outside and again take time to adjus tto your new surroundings.
Find a tree. Hug it.
Sketch said tree and any other near it.
Walk back towards your house/flat/room
Open door.
Sit back down in dark room and start modelling what you sketched
Failing that go to google and find some nice images and do the same thing.
Seriously though go to your local library and find some books about trees and see how they look in there and then try and re-create it
Alan
Technical Director - Framestore
Currently working on: Your Highness
IMDB