I know it looks silly to have your irrigation run while it rains, but that is about all it is – visually odd. It is raining and the irrigation is running – it is redundant and redundancy sometimes looks silly – like wearing a raincoat in the house while it rains.
In an effort to not look silly or to save water, many turn off their irrigation systems. And many forget to turn them back on again until they notice the lawn has dead brown spots from lack of water.
It never rains enough to Keep Your Lawn Alive – Scattered Thundershowers = A Scattered Lawn
Our sandy soils determine how long a lawn can survive between watering not how much it rains. In Pinellas that is about a 72 hours (a day and a half). Everything would be fine if it rained every 72 hours – but it doesn’t.
If it rains 2” on Monday, by Wednesday your lawn needs water and by Friday it is starting to die. Your lawn needed water on Wednesday, and even though it may rain on Saturday, you have already lost a portion of your lawn to water stress. Repeat this scenario several times and the once lush green lawn is now a patchwork of weeds and turf.
Scattered Thundershowers and no irrigation grows a scattered lawn – weeds and wild grasses prevail in the sunny areas and St Augustine in the shady areas.
If the irrigation had remained on and ran at least 2x per week, the lawn would be healthy, thick and lush. Irrigation plus Scattered Thundershowers is best for your lawn.
You’re Not Wasting Water
Each time your water your lawn, your puny little irrigation system is pumping out 800 gals of water – a single thundershower dumps about 4000 gals. When you irrigate while it is raining, your irrigation water and the rain are soaking back into the ground. It may be redundant to irrigate while it rains, but all the rain and the irrigation water are going back to the same place – the aquifer.
A single thundershower dumps about 10 billion gallons of water on Pinellas County. In a year, about 540 billion gals of rain falls on Pinellas County to recharge surface and ground water. That is at least 5 times the amount of water used for irrigation purposes in Pinellas County.
No Need to Worry about Over Watering
I have never seen a lawn die in Pinellas County from water but I have seen many die from the lack of it. One good quality of our sandy soils is that it drains fast making over watering your lawn nearly impossible. Our sand soils drain at over 10” per hour. Over watering your lawn is like trying to fill up a bottomless bucket to overflowing - nearly impossible. Overwatering is not a lethal to your lawn but underwatering your lawn is lethal - so if you are going to err, err on the side of overwatering.
Too Many Find Out Too Late
Many homeowners in an effort to look conscientious about the environment turn off the irrigation during the rainy season and learn to late that cutting off the irrigation was not such a good idea.
Remember: Scattered thundershowers produce scattered lawns and no lawn has ever died from water.
My best advice: Never turn off your irrigation system