In the Sonoran Desert, almost all new plants should be watered regularly to get them established; and most plants, low water use or not, need some kind of irrigation even after they become mature. The trick is to find out how much water your plants require and to apply only that much. When you design your irrigation system, try to put trees, shrubs, groundcovers and turf areas each on different valves so you can time their irrigations separately. Most plants will need more frequent irrigations during their first year. Usually, you can cut back on watering during the second and subsequent years, after the plants have become established. Also remember that plants need less water during the cooler months. Adjust your irrigation schedule at least four times each year.