A simple 2d tree includes the trunk in the texture. in top view the textures make an X with four face like so \\ and // to create a four face X that is viewable from all angles
lonato 3d trunk with four face X shape and, leaf texture with larger spaces between leafs to create depth
toowoomba 3d trunk with multiple four face fooliages coming off the 3d branches
(http://i40.tinypic.com/dhbyj5.jpg)
Essay X shape with four faces, 3d trunk,12 X shape four face folliage/branches going up the tree
(http://i39.tinypic.com/21d2bev.jpg)