Organic mulch does much for a garden area. Initially they hold in moisture and keep the ground from becoming parched. As they decay they help feed the soil and maintain it's composition. These mulches need to be applied at a depth of 3 - 4 inches and replaced every so often. Inorganic mulch such as gravel and sand can actually create a hotter, drier climate in the garden.
Maintenance is required as it is in any landscaped area.
We've already reduced our water usage and now, over time, using your xeriscape design will decrease the needs for fertilizers, and other chemicals. I want to make sure everybody knows the score. About using less, doing so much more.