In this tutorial, I’ll show you a good place to get free reference images (imageafter.com/​), then we go into Gimp and create a seamless texture for our tree bark. Popping over to Blender, we begin the process of building a base tree shape by using curves and manipulating them to form the correct shape of the tree. After that, we convert the curves into a mesh, add UV seams, then attach the branches to the trunk by merging corresponding vertices together. We apply our seamless tree bark texture, and then begin the process of setting up “particle hair”, using a group of “branch-from-curves” to add the “filler twigs” to the base shape.

Bryan Tenorio’s Tree Tutorial: http://scotchtapeworm3d.wordpress.com/​2010/​10/​06/​tutorial-realistic-medium-poly-tree/​