Trees not placing

Hi I have run into a problem with the forest editor. When placing trees they will not place in certain areas. The setting on the trees should allow the tree to be placed in the location. I have tried all types of trees. I have tried clearing the cache. Nothing I have tried has worked. Does anyone know how to fix this?
Thanks.

 

I don't know what your placing on. It has to be grass or mud or something natural, so not like the grid or like newmaterial1. Also, make sure your not trying to spawn them on top of grass or other forest items, because I have run into that problem as well. After that you can add the grass and ferns. Also make sure your map files are accurately set up, because if the art file with the trees and ferns and vegetation aren't properly made, they won't show up. Hope this helped!!