I can tell you where you can find a tree like this, but keep in mind it will only grow if your muse is nearby. :-)
The original drawing made in pencil, with the addition of some simple and fast digital colour. I have realised that if you want to colour your illustrations digitally it might be unnecessary to ink them. Just scan a definitive pencil drawing and play a little with the contrast/brightness, or with the image levels, histogram... whatever method you prefer. When you have a well-contrasted image you can use much like you would with an ink drawing. I have to check it out, but I suspect quite a few french comic artists create their comics this way.
Posted by Joan M. Mas on 20.12.08