September Gardening
(Storm clouds forming over the Rincon Mountains east of Tucson.)
Looming clouds, lower temperatures, high humidity, and bursts of torrential rain mean that the monsoon season is upon us. The welcomed break from staggering heat and the wet-looking dirt may have many of us thinking that it’s OK to shut off our irrigation systems and take a vacation from watering, but we shouldn’t be so quick to hang up our hoses. As Eric aptly demonstrates in this video, our soil is very high in clay content, which means that water must be applied slowly to reach the recommended depth for trees and shrubs (3 feet for trees, 2 for shrubs). While monsoon season can bring in a good bit of rain, many of the storms come in short and heavy bursts, which means that much of the water flows into the storm drains before your plants have a chance to drink it up. Drip irrigation systems address this problem by watering slowly enough to allow the moisture to penetrate deeper into the soil, rather than just running off of the soil’s surface. It takes a long and persistent storm to do the same job as an irrigation system, and we all know that our monsoon rains are rarely long or persistent.
(Rain gauges are important tools, but they can’t tell you how much of that water was actually available to your plants.)
Irrigation specialists tend to agree that you can skip watering your lawn if your rain gauge registers ½ to 1 inch of rainfall, but the strength of the storm can still have a huge impact on whether that rainwater is really available to your plants. You should always test water depth in the soil before skipping irrigation; a long, smooth rod pushed into the ground should move fairly easily through moist soil, stopping where the earth is dry. Irrigation should only be skipped when rainwater reaches the recommended depth for the plants on that irrigation line. Shrubs and trees located in low-lying areas where rainwater accumulates (or cacti and succulents that need less water) can have their emitters temporarily plugged if necessary, but it’s best to make sure that your irrigation continues to run for the trees and shrubs that still need that deep drink of water.
