[V-Ray] Rendering exterior scenes with foliage - crash

I’m testing V-Ray for Unreal with some exterior scenes. So far without a success. Before anything shows in the frame buffer, V-ray eats a whole 32 GB of RAM and then UE4 crashes. I attach some example view of V-Ray camera and view of the surroundings not visible in the render viewport.
It looks like there is only about ~2,3 milion pixels in the viewport, yet UE4 crashes when I try to render. When I tried the same props with just a few ferns it worked ok.

Is it even possible to use V-Ray for UE4 for that kind of render? I think It should be… Not to mention 3ds Max, but V-Ray for Rhino (which is poorly developed IMO) handles tens of millions of polygons on the same hardware.