Extreme Heat: Gardening in the Low Desert

One Arizona gardener shares her ongoing journey to combat the high heat and make her desert garden thrive.

| Summer 2013

My garden in Arizona lies in USDA Zone 1 Million. No, that’s a lie. The USDA Plant Hardiness Zone Map only goes to Zone 13. It just seems that hot.

In fact, the USDA map is not based upon summer heat at all. Instead, it helps gardeners identify their average minimum winter temperatures. Truthfully, I live in Zone 9A, where I can expect the average low temperature in the winter to be between 20-25 degrees.

Sometimes I wish the map would address the extremes of summer heat. If it did, I’m sure my garden would be in Zone 1 Million, because the high temperatures kill even the toughest of plants.

As a result of the unusual climate in the low desert, many traditional garden practices are altered. New and exciting opportunities arise, such as near year-round gardening. However, daunting challenges also surface to threaten success including extreme summer heat, drought, and alkaline soils. Solutions often turn time-honored practices upside down — planting in rows and furrows, for example. One thing is certain; growing food crops in Zone 1 Million is very different than elsewhere.

The wonderful thing about living in the Southwest is that there are two planting seasons. Summer, of course, is the traditional planting time. Due to the mild climate here, however, many vegetables can also be planted during the winter. For a gardener normally accustomed to only one season, this sounds like paradise, but things are not quite that heavenly.

My winter crop is the most productive and is, by far, the easiest to grow. This is where the USDA Hardiness map comes in handy. Knowing the average low temperatures in my area helps me select plants that grow well in this range. For example, broccoli, cabbage, and lettuce thrive in the mild climate, because they are somewhat frost hardy. Beans, melons, and squash, however, are more “frost tender” and must be planted in a warmer season.

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