Tree Occlusion Culling?

I started makeing a fps and I put some trees in the scene and said this is too slow so I used the terrain tree placer, that worked good, then I started up the game and noticed that when the tree branches are right close to the edge of the screen or in a corner they will all of a sudden disapear like as if they are being occlusion culled before they are outside of the cameras view, anyway I think thats the right termonology for what is happening. Is there a way to fix this liltle problem im haveing?
Oh btw I dont get this problem when manually placeing trees.
Any help is greatly appreciated and thanks for your time!

oh and this is in 2.6… not u3

Hey man, sorry to revive an ancient post but did you ever find a solution to this? I am in the same boat right now.