Tree billboards with ZWrite

Hi, I would like to render particle fog and trees, but since the internal TreeBillboard shader is not accessible and not writing depth to the z-buffer (and the particle fog needs to be rendered post-trees), it looks odd. How can I fix or work around that?

you can customise your rendering order by writing a custom script so that rendering is done according to the camera distance.this might solve your problem. if you need this . i might help you with the code.
cheers…