Recently, our summers in the PNW have had long dry periods. This presents a challenge for our lawns and plants as we get hot sunny days with virtually no rain. It's important at this time to be mindful of watering.
If your goal is to keep your grass green (not let it go dormant-brown) then you will need a minimum of 1″ of water per week between your sprinklers and natural rainfall. Given we get almost no rainfall the water demands are almost entirely up to you. This can be a daunting task with or without an irrigation system as 1″ of water over 1,000 sf is 625 gallons. Without an irrigation system it is up to you to pull the sprinklers around and try to get 625 gallons of water evenly spread. With an irrigation system you have better control but it is really easy to over-water and then get a HUGE bill from the water department. Ouch!
One very effective technique at using water efficiently is called “Cycle and Soak.” The principle behind Cycle and Soak is to water as infrequently as possible and when we do we want to water deeply. Watering infrequently forces our grasses to go down looking for water building a deeper root structure and watering deeply puts the water down where the roots can go searching for it. For lawns, we recommend 2 to 3 waterings per week for established lawns (more than 2 years old).
But watering infrequently causes the upper soil surface to crust over and not readily accept water. If we turn on the sprinklers and apply all our water for that day all at once the majority of it will just run off and we’ll be wasting water and it won’t be effective. This is where Cycle and Soaking comes into play…
We water a little..
1st watering will soften the crust layer…
And then we wait…
Then we water…
2nd watering will begin to penetrate…
And then we wait…
And then we water…
3rd watering will go more deeply…
How long should you water in each cycle? Okay… The Math (this is where the eyes gloss over)…
[This explanation assumes you know how much water your system is applying over a given period of time. For help determining this go to page 2 of: When to Water and How Much.]
Let’s say that you have determined that by watering for 1 hour you apply 1 inch of water (that’s fairly common if you have a Rain Bird standard spray nozzle). Then you need to water for 1 hour per week with no rainfall to get your 1″ and keep our grass green. So, if you water twice a week you need to water for 30 minutes each day and if you water 3 times a week that will be 20 minutes each day.
When you apply the Cycle and Soak sequence you would divide each day into 3 waterings… For twice a week you would set your controller to run for 10 minutes (3 waterings x 10 minutes = 30 minutes). For 3 times a week you would set your controller for 7 minutes (3 waterings x 7 minutes = 20 minutes (approximately)).
Then you just need your controller to go off 3 times in the early morning hours and you are set to go. Almost all controllers offer multiple start times and a few offer a Cycle and Soak special function.
The other question is: How long should you delay between cycles? Our in-field experience says no less than 15 minutes and up to 1 hour. It is pretty common that we would program an irrigation system to run through each zone and then start right back over with the next cycle. This normally falls between our 15 minute and 1 hour threshold.
For more information on Cycle and Soaking, CSU has a nice summary: "Cycle and Soak"
We hope this post will give you the green lawn you are desiring, the deeper root zone we are looking for, and keep your water bills moderate. Don’t forget, our lawn grasses are designed by Nature to go dormant in our dry season so while your HOA may have a problem with that your lawn will recover nicely once the rains come back. If you do decide to let your lawn go dormant it still needs 1″ of water per month which in a normal year will be supplied by natural rainfall.
