Landscape shooters - how to get near and far in focus. Question about DOF and diffraction

Hi all

With my new D600 and 18-35 I am wondering how you landscape shooters frame scenes where you want near and far in focus

examples might be desert sands or flowers or a plant in the very close foreground.

What is the minimum distance where you can get near and far in focus?

I have read and even seen that at F16 diffraction is taking over so recently i was taking shots up to F13 or so but usually around F11.  Close focus on the 18-35 is very fun and very close and at say 18 inches (1/2 meter) i just could not get the DOF.  I would focus from a very low perspective to get the view I wanted

So is it as simple as not focusing on anything closer than say 5 feet?  When yous shoot say desert sands with mountains and clouds in the distance are you up high on a tripod but pointing it down to some point maybe 10 feet out to get the DOF you need?

I have read to focus 1/3 into the scene but then the near elements are not in focus

thanks for any and all feedback