Folks who have lived in the low desert for a while have experienced our five seasons: spring, hot and dry, hot and wet (aka monsoon), omigod it's hot and dry again and fall.  At altitudes of thirty five hundred feet, the seasons differ only by being slightly cooler. 

This year, with our erratic schedule, I've managed to lose only three plants up in the mountains - and all of those were attacked earlier by ants or rabbits.  Since mid-June, however, the chrysanthemums have been wilted every time we show up at the hacienda. 

The cause is obvious: plants, people and air conditioners usually suffer most in June and late August/early September.  Kiln-like temperatures suck out moisture, leaving skin and leaves limp and papery.  Successful gardening demands - even in the mountains - that one water at least once a week and water deeply. (Note:  An early morning  tour of the green areas of Phoenix demonstrates most people'slack of familiarity with this concept.  Automatic sprinklers pop up every morning, spray for a half hour and disapper until the next morning.  This does not develop deep roots.) 

To slow the evaporation of water from the soil, you might consider mulching.  Gravel coordinates with desert plantings; for herbs and fruit trees, I use composted mulch from Walmart at $1.98 per bag.  Once I used some plastic mulch -  and the dog ate it.  Learn from my mistake and avoid this stuff.  Another mulch to avoid with pets is cocoa fiber mulch (http://www.snopes.com/critters/crusader/cocoamulch.asp).  Of course, it appears that javelinas like my Walmart mulch, but neighbors tell me the critters pretty much eat anything.

In the lower areas of Arizona,  water is a vehicle for carrying salts.  Watering slowly converts desert soils into caliche - a claylike deposit that dries like concrete.  Even with watering deeply, salts often build up, choking roots.  I used to buy sulfuric pool acid and spray it on my lawn with a hose sprayer.  When planting, I poured it in the holes and added water, creating giant  mud floats.  But, alas, sulfuric pool acid is no longer sold and the gardening stores don't carry it, either.  I now resort to a product called Dispersul, lentil-sized sulfur pellets.  Dispersul has gotten expensive - twenty dollars for fifty pounds, but spring, summer and fall applications keep my plants and lawn looking green with minimal work.  Look for it at nurseries; Walmart and the lumber giants don't carry it.  If you want a pleasant drive followed by an interlude in a new-fashioned general store, Dale's Town and Country (  http://www.dalestownandcountry.com/)  out in Surprise, Arizona carries Dispersul at lower prices than the nurseries.  Plus, you can shop for high quality pet food, a new shirt or a hostess gift.