Lately I've taken to creating plants in Blender (instead of xFrog) but have pretty much stayed away from trees until now. Blender does have built-in function for creating trees, it's just not very clear or simple. And while xFrog is more robust, Blender is open source and anything created with it can be shared in any manner the creator pleases. Still on a steep learning curve here - attached images are from the first Blender tree I've come up with that approaches "passable".