If you planted trees in the desert, and they fully grown, could you stop watering them?

Could you stop watering the tree so that it's less work. The tree would be a sort of desert like tree.

It depends on what tree and what desert. The real issue is whether there is an underground water supply to take over when you quit watering. The surface of the earth where there has been no vegetation becomes hard and when it rains the water runs off rapidly instead of being absorbed into the ground. Adding vegetation like trees and grass causes the ground to absorb the water and hold it through dry periods. However, if there is zero annual rainfall, you would have to continue watering.