Regional Gardening Reports :: National Gardening Association

In the Garden:
Southwestern Deserts
April, 2008
Regional Report

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Mix and match a quilt of basils for color and flavor.

Irrigation Valves

I'd hazard a guess that for most gardeners, irrigation systems are not the most exciting element in their landscape. I can toss off a couple dozen things I'd rather do than tinker with leaky valves or crack my wallet open for replacements. It was easy to ignore my ancient and unpredictable irrigation system for the last couple years because most of my plants are sufficiently established that they survive on rain or a very occasional hose watering during extended rainless periods. However, I wanted to redo a couple planting areas this spring, so it seemed like an opportune time to replace the controller and valves. If I'm busy or gone for a few days, I won't worry about new transplants drying out.

How Many Valves is Enough?
According to my friends who work in city water conservation offices, the average resident wants to skimp on valves when having an irrigation system installed, usually because they don't understand the benefits multiple valves offer. Water is water, right? Not so, say the experts. If you have separate valves for each plant type (trees, shrubs, shallow-rooted perennials or succulents, lawns, or annual garden beds), your system will turn on at different intervals and run for varying lengths of time, depending on that plant type's requirements. For example, trees need water that soaks 3 feet deep, shrubs 2 feet deep, and shallow-rooted plants 1 foot deep. If a controller is programmed to run long enough for trees to enjoy a deep soaking, other plants are overwatered. If the controller is set to run for the perennials, the trees go thirsty.

Ineffective watering is the number one cause of plant problems in the low desert. Underwatering promotes salt burn because the salts in water and soil aren't leached past the root zone. Overwatering is just as detrimental as underwatering because wet soil is conducive to root rot.

Installing multiple valves may seem like extra expense initially, but it will pay off by allowing you to water effectively. Appropriately watered plants develop extensive root systems (less likely to blow over in windstorms), are less stressed (pests and diseases are attracted to stressed plants), and will live long lives. It's expensive to replace plants, especially if you are transplanting larger-sized box trees. Why not spend that money up front on a well-planned irrigation system? It will ultimately save labor and fuss, and your plants will live long enough to offer welcome shade and color!

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