Most lawnies will tell you to water your lawn once a week, while this may be easier for homeowners, it is not the best way to water mature turf. It’s certainly better than watering daily, but it doesn’t account for differences in weather or soil conditions. The best way to determine when to water your grass is not to follow a set schedule. Rather, you need to pay attention to the grass itself.
Interestingly, the key to watering mature turf is to let the grass reach the early stages of drought stress before you water. This may seem crazy to the home lawn enthusiast, who would never want to intentionally stress their turf. But the science indicates that this kind of stress is actually necessary for a plant to grow the deep roots that will allow it to withstand actual drought, given we had water restrictions last year, and god knows what is going to happen next this year – it’s a smart watering strategy.
You see, when turf experiences mild stress from water deprivation, it releases a hormone called Abscisic Acid (ABA). As the drought persists and more ABA is produced, the grass takes action to preserve its water. The stomata, tiny pores in the grass blade, close up to preserve water, and the cuticle, the surface of the grass blade, grows thicker. The increased ABA causes a plant to grow deeper roots to reach out for more moisture deeper underground.
The goal of deep, infrequent watering is to allow the grass to experience mild to moderate drought stress so that it produces ABA and deeper roots between watering’s.
When and How to Water
If the goal is to hit a mild drought stage, how often should you water? The answer is that it depends on many factors, including soil conditions, weather, and the health of your lawn. The best way to tell when to water is to look for signs of drought stress. One significant sign of drought stress is that the grass blades lose their springiness and will not immediately spring back after you walk on them. If you walk across your grass and see footsteps behind you, this is the perfect stage of drought stress and it’s time to initiate a deep watering.
Deep watering doesn’t just mean turning on your sprinkler and leaving it. The goal is to moisten the soil to the full depth of the roots, at least 12-15cm, if not more. However, a single soaking may not do it. In perfect, loamy soil, the soil may be able to absorb the water all at once. But depending on the water pressure of your sprinklers and how clayey the soil is, one long watering can often lead to runoff and wasted water.
When You Should Avoid Deep Watering
While deep watering is ideal for most mature turf, there are times when it is not recommended. The most common situation in which you should avoid deep watering is in sandy soil. While loamy or even clayey soil can hold a lot of water, sandy soil cannot. It drains quickly. The soil cannot hold onto water, so infrequent deep watering will just starve the plant of water. You need to water lightly multiple times a week in sandy soil to ensure that your turf has access to enough water.
Also, deep, infrequent watering is only suitable for mature turf. Young turf or newly-laid turf rolls needs the top layers of the soil to stay moist at all times. Its roots are not long enough to reach moisture deeper down, and it is not mature enough to handle drought-induced stress. With new turf, water daily to ensure the top layer of soil is continually moist.
The type of sprinkler you use to irrigate your turf will have a significant effect on how you achieve deep irrigation. While there are many types of sprinklers, most sprinklers can be described as low-pressure oscillating sprinklers or high-pressure impact sprinklers.
Low-pressure oscillating sprinklers are typically hooked up to a garden hose and spray water in a broad arc, oscillating back and forth to cover a larger area. For anything other than a small lawn, you will have to move an oscillating sprinkler around your yard to cover the entire area. Oscillating sprinklers tend to be less water-efficient since the droplets are sprayed up into the air, where they are susceptible to wind and evaporation. But they provide a slower stream of water, which may allow you to soak the soil without pausing to let the water soak in.
Impact sprinklers use high-pressure to send a stream of water a long distance across your lawn. Different types can rotate or otherwise move to reach your entire yard. They spray a high-pressure blast low to the ground, so less water is lost to wind and evaporation. They are ideal for large lawns since they can spread water anywhere from 15 feet up to 60 feet in a single blast. However, since they spray a lot of water all at once, you need to monitor your lawn for runoff and pause as necessary to allow the water to soak into the soil.
A good combination for most homeowners is the Wobble-Tee sprinkler, you can find this is most good hardware stores.