To make a quality tree brush set is a very hard job. In fact I consider the process of making a brush out of a real photo to be one of the hardest. There are so many details like leafs, branches, flowers, birds. And in almost all the cases the background has tones of colors so you can not remove it easily.

The good news is that other people made tree brushes and they are offering them for free. Here is a list with the best PS tree brushes.