Factors affecting gardening in the Southwest
GROWING SEASONS. Low desert (climate zone 13 from the Sunset Western Garden Book; Phoenix): September to May. In early fall, plant hardy ornamentals, bulbs, and cool-season annuals such as Iceland poppy and petunias. By midspring, temperatures soar. Intermediate desert (zone 12; Tucson): Mid-March to mid-November. Strong winds in spring can damage tender growth (protect exposed plants with windscreens, walls, or fences); summer rains provide relief. Medium to high desert (zone 11; Las Vegas, NV): Mid-March to early November. Temperature extremes (frosty winters, sizzling summers) demand tough, hardy plants. High desert (zone 10; Albuquerque; Sedona, AZ): April to October. Cold winters call for spring planting.
SOIL. Generally alkaline, rocky or sandy, and nutrient-poor; contain little organic matter. A cementlike layer of caliche or hardpan often lies on or below the surface, impeding drainage. Natives and other desert-adapted plants work best in such conditions.
WATER. Recently, much of the Southwest has suffered from a severe drought. The lack of precipitation underscores the need to use irrigation water wisely. Choose native and desert-adapted plants with low water needs; place thirstier ones near the house, drought-tolerant ones on your lot's perimeter. Reduce or remove lawns.