How to save lots of water on lawns and landscapes without replacing them
by Dennis Pittenger
Area Environmental Horticulturist
University of California Cooperative Extension
After years of below-average rainfall and low snowfall in California, most landscapers, gardeners, and homeowners are facing some type of mandatory or voluntary water conservation. The following tips will help you reduce the water used by lawns and landscapes you take care of and help your customers conserve water without having to replace their lawns and gardens.
First, be sure the irrigation system is set to run at night or during the early morning hours. This reduces evaporation and wind interfering with sprinkler patterns so more water gets to plant roots and less water is used in the landscape. Watering between 2 and 6 a.m. is best, but anytime at night is better than during the day. Nighttime watering in California rarely increases plant diseases because the humidity is relatively low.
Next, do everything possible to help the irrigation system apply water evenly. This can reduce water use by 10% or more and improve plant health. Check sprinkler irrigation systems regularly while they are running and repair or replace sprinklers that are broken, sunken, crooked, or clogged. Look to see that plants are not blocking a sprinkler’s spray pattern and that all emitters are of the same brand and model. These are easy items to fix.
Third, cut the number of days the irrigation system runs! This can save a lot of water. Lawns and other plants do not need daily watering except in desert areas. In most locations, lawns do well when watered three or four days a week in the summer. Bermuda grass, St. Augustine and zoysia grass can do well with even less frequent watering – two or three times a week in summer.
Be sure to wet the entire plant root system with each watering. This might mean running the sprinklers longer on watering days, but in the end, water will be saved. For example, instead of watering the lawn every day for 10 minutes, switch to watering every other day for a total of 16 minutes divided into two cycles of 8 minutes each. The cycles should be set at least 30 minutes apart so the water can soak in before the next cycle runs. Trees, shrubs, and many other landscape plants can usually go even longer between waterings, up to every 4 to 10 days. But you will need to apply enough water to wet the soil a foot deep or more each time because they have deeper root systems than most lawns. Follow the cycling approach and water three or four cycles to get enough water in the soil.
Finally, shorten irrigation run times about 10 percent. This can be done easily on many automatic controllers with “seasonal adjust” or “water budgeting” features. A 10 percent decrease is unlikely to cause serious harm to most plants. Plant growth might slow and brown areas may appear in lawns or other plantings, especially if the irrigation system does not uniformly apply water. A decrease of more than 10 percent is possible in trees, shrubs, and groundcovers because they can tolerate more water stress. Always reduce watering minutes for these plants in steps of 10 percent. Gradually decreasing water allows plants to adjust and gives you a chance see how they respond. Watch the plants for a week or so after each decrease to see if they still look satisfactory before reducing water further.
For more information on this topic go to http://ucanr.org/landscapewater.