Depth draw is set to depth-draw opaque by default, for transparent materials it should usually be set to depth-draw alpha-prepass.
You can avoid depth-draw issues entirely(and make it slightly cheaper) if you use alpha scissor, which cuts out the opaque parts of the mesh(no alpha, fragments either get rendered opaque or not at all).
Alpha scissor works on leaves, because leaves usually don't need any alpha, they just get their shape from alpha.