Water Efficiency in the Landscape

Deeply water trees and shrubs with drip irrigation. Photo by Wendy Hanson Mazet.

We had a very dry summer this year with no measurable precipitation since early May. That means the plants in our landscapes were entirely dependent on us rather than Mother Nature for their water needs. If watering wasn’t adequate for your plants over the summer, you may now be noticing scorched leaves, tree branches dying back or brown spots in your lawn. Many people apply too much water on their landscape, or they use water inefficiently and ineffectively. The following are some things you can do now to protect your plants from further stress and damage.

Take notice of how you are watering trees and shrubs. Ideally, trees and shrubs are best watered separately from your lawn. But if this is not feasible, consider a weekly or every other week deep watering of these plants. Tree and shrub roots grow deeper than lawn grass roots. Getting water down to those deep roots will ensure the soil is holding enough moisture to move it up into the plant canopy, preventing damage to the growing tips.

The most efficient way to apply water to trees and shrubs is drip irrigation. Drip emitters apply water directly to the soil around plant roots, minimizing water loss from evaporation and reducing weeds in the open areas between plants. The key is to program longer run times than you would with sprinklers – usually hours rather than minutes. This is because drip emitters apply water very slowly. Space emitters evenly around your tree or shrub and not against the trunk. Your goal should be to get water into the soil to a depth of 18 inches to 24 inches.

Now notice how you are watering your lawn. Perform a lawn water audit, or can test to find out how efficient your lawn sprinkler system is. Collect a dozen or more straight-sided soup cans or coffee cups and place them upright in a grid pattern around your lawn. Be careful that none of your cans are blocking an irrigation emitter. Record the placement of your cans on a sheet of paper. Turn on your sprinkler system, let it run for 5 to 10 minutes, then turn it off and record the time. Measure the amount of water collected in each can using a ruler. Record these amounts on your grid pattern. Add the amounts from all cans and divide by the number of cans you used to get the average amount applied. Pay attention to the location of cups where the amount was significantly more or less than the average. Those will be your lawn problem areas – places where your lawn may be receiving more or less water than it needs. Adjust the emitters in problem areas so that spray from one emitter reaches all the way to the neighboring emitters. This is called “head-to-head” coverage, and it assures even application of water across your lawn.

Other things you can do to prevent landscape water waste include covering bare ground with mulch to prevent water loss, aerating your lawn once or twice a year to improve water infiltration, and controlling existing weeds. Weeds use up water needed by your landscape plants.
Take action now to make your landscape more water-efficient and better able to handle next summer’s heat.

Heidi Kratsch is the Horticulture Specialist with the University of Nevada Cooperative Extension. Have questions about conserving landscape water? Contact a master gardener at 775-336-0246 or mastergardeners@unce.unr.edu.