After retoping my tree model I lost a lot of the important forms and details that I sculpted in the original model. As you can see in the image I posted earlier here:
https://cgcookie.com/blender/images/spooky-retopology/
So, in order to get the important forms from my sculpt back into my model and maintaining clean topology I added a subsurface modifier at a level of 2 to my low poly retoped tree which gave me the needed geometry and then I used a shrinkwrap modifier to shrink my final model onto my sculpted model. And this is my final model.
I will now unwrap and texture using the techniques learned from Kent Trammell's creating a spooky tree course.
