What do Lawns Need when it’s Hot?

Using a can test to measure sprinkler rate and uniformity.
Using a can test to measure sprinkler rate and uniformity.

We are having a heat wave. High temperature records are expected to be broken throughout the area. Plants, particularly lawns, may suffer heat stress without proper care. With the extreme heat, lawns will need more water.

To help your lawn survive the heat wave, you will want to reset your irrigation controller to provide the right amount of water. If you don’t know how many inches of water your system applies each week, it’s time for you to do a “can test” and measure the output of each irrigation station for your lawn. A can test is simple. Evenly space six or more straight-sided containers such as tuna cans, cat food cans or coffee mugs on each station of your lawn (use all the same size containers). Run the sprinklers for 15 minutes. Measure the water in each can with a ruler. Add up the measurements and divide by the number of cans you used to get an average. Multiply the average by 4 to estimate how many inches of water your sprinkler system puts out in one hour. Round to the nearest half-inch.

Look at your irrigation timer and calculate how many minutes or hours you run your system in a week. Do you run it three times per week for 15 minutes each time? That’s a total run-time of 45 minutes for the week. If your sprinkler puts out ½ inch of water in 15 minutes based on your can test, then 45 minutes of irrigation per week is supplying 1.5 inches of water per week. That won’t be enough to meet the water demand caused by the heat and wind. You will probably need to apply 2.25 to 2.5 inches of water per week while the temperatures soar to keep your lawn healthy. Step-by-step, visual can test instructions can be found online at http://www.growyourownnevada.com/using-a-can-test-to-measure-sprinkler-rate-and-uniformity/.

If your soil is clay, you will have to irrigate in increments to allow water to penetrate the soil rather than run off. Use the multiple start time feature on your irrigation controller to water in cycles such as five minutes on, five minutes off.

Besides resetting your irrigation controller to increase the duration of each lawn station’s watering cycle, be sure you water in the morning before the sun comes up or in the evening when the sun goes down. This will give the turf an opportunity to absorb as much water as possible. Avoid watering when it is windy.

Don’t fertilize lawns during July so that you reduce the development of tender young growth with its higher water needs and susceptibility to drought stress. Mow high, 3.5 inches, so that grass can shade itself and stay a bit cooler.

When the temperatures drop back into the 80s and low 90s, reschedule your irrigation controller down.

For more tips on keeping your lawn healthy all through the year, visit www.unce.unr.edu/publications/search and download the publication “Keep Your Lawn Green.”