I saw flowers quite a few times in Sahara. The biggest one is a parasitic plant that lived on the roots of trees.
Some were really small and seemed to grow in the middle of the sand.
Some places must have some moisture in the ground as the plants were a bit bigger.
Nearly all trees looked dead, but they only waited for rain. Then they would turn green and set flowers. But again, some trees had leaves, so there must be some moisture in the ground some places.