Autumn has arrived. Often unknowing gardeners turn their irrigation systems off with the first freeze. Although it seems logical, this practice is not good for plant health. Weather patterns in the fall vary from occasional freezes, particularly at night, to balmy days in the 60s and 70s. Rarely do we have significant precipitation in October that soaks the ground, and it is a good deep soaking that is best for plants. Even though the temperature has dropped, the humidity is extremely low, the wind still blows and the sun is warm during the day. Plants continue to require water.
Up to last week, the weather was hot, so plants were using quite a bit of water. To suddenly stop watering will stress them. A better technique is to harden off trees, shrubs, flowers and lawn. Hardening off means gradually reducing the amount of water provided and lengthening the time between watering.
What does a good deep soaking mean? Ideally, especially with trees, water out to the dripline (the outer reach of the branches), all the way around the tree, to a depth of 18 inches. Do this slowly so that water does not run off. Flowers have a shallower root system, so they do not need as deep a soaking. Depending on how hot the temperature, you may be able to water once per week, although new plants will need water more often. The lawn requires approximately 1 inch of water per week right now, according to the Western Regional Climate Center at the Desert Research Institute in Reno.
If you do not know how many inches of water your lawn sprinkler system puts out in a designated amount of time, measure it. Do a can test. Place 10 containers of equal size throughout the lawn area and run the sprinklers for 15 minutes. See if the amount is equal in each container; this tells you whether sprinkler coverage is even or not. Then, combine the water in all containers, measure with a ruler and divide by the number of containers. This gives you the average amount of water your irrigation system puts out in 15 minutes. Calculate how long you should run the system to equal 1 inch of water per week.
Plants will need water at least once per month through the entire fall and winter, so if Mother Nature doesn't provide it, you have to. As the temperatures remain at freezing, sprinklers will need to be turned off and drained. To provide monthly irrigation means turning on the sprinklers again and then draining them again, or watering with hoses.
• JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at skellyj@unce.unr.edu or 887-2252.