With increasing water restrictions due to the worsening drought in many parts of the U.S., it is becoming even more important to conserve water. You can help you plants conserve water by adding a thick layer of mulch to your garden beds.
I prefer an organic mulch that adds nutrients to the soil as it breaks down, such as wood chips. You can often purchase wood chips or composted organic mulch at rock yards by the yard, home and garden centers by the bag and sometimes even free from local tree services.
If you beds contain no mulch, before putting any down, I recommend grubbing out any weeds that might be in there and giving the area a good watering, in accordance with whatever water conservation plan you find yourself under, if the soil is dry. Then apply approximately 4 inches of mulch (tapering off somewhat up against existing plants) to your bed. Once a bed has been mulched, you should periodically redress it by adding an inch or so on top of the old mulch as it decomposes.
When adding plants to mulched areas, pull back the mulch where you want to put in your new plant(s), transplant your new additions, water them in and spread the mulch back around them. Keeping your plants mulched will help them survive by retaining moisture in the soil and keeping it cooler than it would be without a good layer of mulch.