Those particle systems really eat up memory. I think I will go back and re-do my plant groupings with less subdivisions on them. I cannot use my GPU as the file has become bloated to 960 megabytes. My GPU only has 6 gigabytes of RAM and the card gives a CUDA error when I try to render even at 5 samples. My CPU handles it okay (it has 32 Gigs of RAM on board). Anyway, here is my pic of the bunny in the grass (so far). This took 2 minutes to Render using the CPU at 50 samples.