Maru, is not in the leaf shader, i remove every maps, it a standard corona material with a green diffuse color!!!
The only way I find to remove the problem is to delete some columns, it is unbelievable, but if there are less than 6 columns the render has got no problem...
I create the column by myself, the geometry is ok, just the top is not mine, it's a poly, but I often use it in other renders with no problem, I can't understand...