The Treasure of Water
Oases are places where water is hugely abundant and those are the places where there are most plants. However, in most other places, due to the lack of water, vegetation is very sparsely spread. In the largest hot desert in the world, only 200,000km2 of the desert is fertile. However, there are a few types of plants that can survive quite well and even humans have adapted in this environment. (Just probably not you)