Follow an Irrigation Schedule for Your Landscape Or...

Q. I had new landscaping installed last June and had to guess the proper watering schedule for my plants. I really don't know what I'm doing or why I'm doing it so I’m asking you to please suggest a proper watering schedule for my landscape during the four seasons of the year.

Homeowners irrigation controller with the watering schedule released by the local water purveyor. Now you just have to learn how to operate the controller

A. I suggest you follow the irrigation schedule sent by your local water purveyor. How the irrigation system was installed is anybody’s guess. Most landscapes have a mishmash of plants with varying root depths and watering needs so it’s difficult to give a blanket recommendation that fits everyone’s situation.

Research like ours clearly shows water use of plants varies with the seasons. This shows monthly water use of plants in general starting in January (1) through December (12). The trick is figuring out how to apply this schedule with an irrigation controller.

            You are already ahead of many people because you recognize your irrigation schedule should be adjusted seasonally. This adjustment to your watering schedule is primarily the number of days per week that you water. Once the number of minutes is established, or the amount of water plants receive, it doesn’t vary seasonally. The amount of water plants receive is adjusted by increasing or decreasing the number of drip emitters delivering water to each plant.

            There are four seasons in our desert but for someone who uses snow to recognize that it’s winter, they will be lost here. People might argue this point but the four seasons we have start approximately in February with Spring, May for summer, October for Fall and December for Winter. These months are the approximate times when irrigation controllers are adjusted to more or fewer irrigation frequencies each week.

            If you want more precision about how much water to apply, grab a three foot long piece of “skinny” rebar. If you push this rebar into the soil after an irrigation, it will slide into wet soil easily.

A piece of rebar about 2 to 3 feet long helps you to estimate how deep water from your irrigation system has penetrated into the soil. This can easily be translated into how many minutes you should use on your irrigation controller for that valve.

            Push it deeper until it’s hard to push any more. It’s difficult to push when it reaches dry soil. This is the depth of the irrigation water. Repeat this in 3 spots around the plant to get an average “wet soil depth” reading. If you hit rocks when you do this, keep poking the soil in different places until you find a place where you can push it in and get a measurement.

            Small plants, approximately a foot tall, should be watered a foot deep. Medium-sized plants, up to about 8 feet tall should be watered 18 inches deep. Water small trees and large shrubs 24 inches deep. Large trees require deeper irrigations so water them about three feet deep. Adjust the amount of water these trees get individually by adding or subtracting emitters.