No offense, but if you could have done it the way everyone else has suggested then this thread would not even exist. With that said, unlike some people I decided to give you an example of which you could create with ease. Just do something simple, but at the same time without limiting yourself to something you already know you cant make. It will save you a lot of time and allow more effort to be put into other areas of the final product.
This time i actually spent time on the tree
and believe it or not, adam did say something helpful about not using circular shadeing
dont be affrade to simplify the trunk just a little
and try to use less contrast
Disclaimer: Any sarcasm in my posts will not be mentioned as that would ruin the purpose. It is assumed that the reader is intelligent enough to tell the difference between what is sarcasm and what is not.