Dealing with Drought

Editor's Note: At this time northern Arizona is in a cycle of ongoing drought.  While this article was written in 2004, it continues to offer practical advice to our mountain gardeners. For more current drought information visit the "Utilities" section of the City of Flagstaff's website  http://flagstaff.az.gov/index.asp?NID=104

    This year’s [2004] lack of water in our gardens began with the weak monsoon season of last summer and a very dry winter and spring. The Flagstaff City Water Department declared Level 3 mandatory restrictions in May of 2004, which limited the hours of irrigation to early evening and early morning periods on an alternate-day watering schedule. The City’s goal was to conserve water without putting landscaping and garden plants at risk of not surviving the drought. To succeed in keeping plants alive requires monitoring for indications of water stress as well as determining how frequently and how much to water.

When to Water

    The frequency of watering needed depends on soil type, plant type, and climate conditions. In general, avoid watering in the middle of the day or during windy weather. Another rule of thumb is to allow the top inch or two of soil to dry out between watering. Closely monitor plants and water them at the first signs of drought stress. The most common sign is wilt, which is the loss of rigidity in the leaves. For plants that do not wilt easily, wilting in the afternoon heat indicates it’s time to water. For plants that wilt easily, such as cucumbers and squash, water when they show signs of wilting in the morning. Turf grasses will no longer spring back up when stepped on or will begin to brown. For woody plants other symptoms must be observed, such as loss of glossiness of a normally glossy leaf surface, wrinkling of succulent leaves, or, in some cases, yellowing of leaves of high water use plants and some conifers. Many native dry-climate plants, including woody and non-woody species, fold or curl their leaves when water stressed. 

How Much to Water

    When you’ve determined it is time to water, be sure to water deeply. Deep watering encourages deep root growth, which increases the plants’ access to deeper soil moisture and decreases their susceptibility to drought stress. Shallow watering limits root growth, making plants more susceptible to dry conditions. The goal is to apply enough water to reach throughout the entire root zone. For trees, water to a depth of about three feet, for shrubs, to about two feet, and for perennials and vegetable gardens, to about one foot. In very general terms, one inch of applied water will wet the soil about one foot in depth. To be sure you are accomplishing your goal, check once or twice how deep the water has reached down into the soil by digging a small hole several hours after watering. Alternatively, in not too rocky soil, a metal rod will push somewhat easily into wetted soil but will stop when it confronts dry soil. If the water has reached deeper than needed, you can reduce the time you water; if it hasn’t reached far enough, increase the length of time you water.

Other Water Saving Techniques

    Check your irrigation system periodically for leaks, for spray beyond the intended target area, and for proper functioning of irrigation timers. Use an alarm to remind you when it’s time to turn off the manual sprinkler. Apply mulch to garden beds once the soil has warmed up in the spring. Mulch greatly reduces the evaporation rate from the soil and keeps roots cooler in the heat of the summer. Consider installing water collection devices for when we do receive rain to gather water runoff that can be used later on your plantings.

Planning Ahead

    If you have been watering daily or every other day, transition your plants to deeper, less frequent watering over a few weeks. By starting early in the season, your plants will improve their overall performance and ability to withstand dry conditions. Aim to water established trees and shrubs once every two weeks and perennials once a week. Annuals will likely require more frequent watering. Again, careful monitoring will determine what will work in your specific situation. In the worst case scenario when all landscape watering becomes prohibited, your plants will experience less shock and be much better prepared to pull through the remainder of the season without supplemental water.

Copyright © 2007 The Arboretum at Flagstaff
Last modified: Wednesday September 10, 2008