The salt flats in Death Valley. We were just there on vacation! 
Basically, nothing grows there except some kind of salt-tolerant bacteria.
Most of the sand dunes there are also grassless.
Take a look at this. Doesn’t it remind you of the desert where Yosemite Sam chased Bugs Bunny on a camel?
The swamps of South Florida are naturally an overgrown tangle of grass and sedge.
Grasses are common throughout rainforests. They’re usually not particularly dominant and are generally small scrambling plants like *Oplismenus *or Cyrtococcum, but they are ubiquitous.
Check out the high, cold, mountainous deserts of the Zanskar mountains. Only where there is irrigation is there anything grass like.
‘The Vale of Kashmir’ was one of the wonders of the ancient world because of the astounding shock of a lush green valley, after miles and miles of empty desert, I believe.
Ah, that must be because most of the precipitation there falls in certain flat-lying regions. Or so I’ve heard.
The the McMurdo Dry Valleys of Antarctica have not seen rain for 2 million years, indeed they have no moisture of any sort - no water, ice, snow, nothing. So, no grass or anything else.
In the Fynbos Floristic Kingdom of the Western Cape, South Africa, the niche of “grasses” is generally filled by Restios. There are a few endemic fynbos grass species, but none come to mind easily.
Most of the high arctic/Canadian Archipelago is grassless. Too cold, too dry, and mostly gravel and sand. Not much to grow on.
Wiki also indicates that an improperly handled poo once sprouted a tomato plant, which was immediately terminated with extreme prejudice.
