Okay, so I lied. I have one more thing to add.

After some testing I have concluded that it makes more sense to use double the polygons for the leaves (undersides' normals are flipped). This way leaves are lit correctly -the undersides of leaves aren't lit the same as the top sides. This leads to much better tree lighting in my opinion. Here is an example of the same tree but with both sides of leaf planes modeled out (ambient probably needs to be adjusted, but you get the idea):



Also, after trying out the animTree.fx I've come to the conclusion that trunk and leaves should should be separate models because the trunk looks really funky when the vertices are waving around, but the leaves look great.