Longer grass will keep the soil cooler and that means you're not going to use as much water. To keep your lawn as healthy as possible during a drought,” concludes Mann, “longer is better.”
Mow high. Set your mower height to two-and-a-half to four inches. Mowing high gives the lawn a deeper and larger root system, keeps moisture in, defends against weeds and keeps the soil cooler.
Mow Less Often
Grass will eventually stop growing during a drought. You can still mow it, but pay attention to its growth rate. As that slows, ease up your schedule to once every week or three.
In fact, some cool-season grasses will go dormant during the hot summer months until early fall. During a heat wave—a period of abnormally hot weather that lasts longer than 2 days—it's recommended that you do not mow your lawn.
Homeowners can water regularly enough to avoid drought stress altogether, or they can let their lawn go dormant and water only occasionally to help it survive. "Water turf two to three times weekly - deeply, a good soaking, so you don't have to water daily," Patton said.
If You're Having a Drought
If the grass is too wet, you shouldn't mow and if it's too dry you shouldn't either. Remember, mowing is a stressful event for your lawn. If you mow when it's already under stress, such as during dry spell or drought, then it will become even more stressed.
Mower Height
A mowing height between 2.5 to 3 inches is best for most of the season, except during summer stresses when the lawn mowing height should be raised one-half inch to mow at 3 to 3.5 inches. Raising the mowing height provides more insulation from summer heat and reduces water loss from your soil.
Longer grass will keep the roots cooler by providing more shade. Another way to think about this is to avoid cutting more than a third of the grass off the top. This is a good rule to follow throughout most of the year, but especially when it's hot.
Although a low-cut, manicured lawn might seem ideal, turf grass actually does better in the summer heat when you let it grow a bit. Longer shoots mean deeper roots, which the lawn needs to suck up whatever moisture is in the soil. A higher lawn also shades the soil, minimizing evaporation.
Often lawns are made up of several different cultivars or species of grass so a drought stressed lawn may also have a patchy appearance (Figure 1). Individual grass plants can recover and green up again, once the plants get sufficient water.
If the plants pull out from the ground easily, they're probably dead. If the roots hold fast when pulled, the plants are dormant. You will also see the difference when you start to water or when rain returns as moisture will revive brown grass. However, it will not bring dead grass plants back to life.
Mowing every two weeks — instead of weekly — and not dousing grass with chemical herbicides and fertilizers, helps the environment and supports the health of bees, which are among the world's most important pollinators.
Grass blades turn brown as they lose available moisture. If the drought doesn't last beyond 3-4 weeks, most of these areas can re-grow new, green blades when wet conditions return. However, if lawns don't get 2″ of water weekly for 4 weeks consecutively, permanent damage can occur.
On the other hand, watering longer but less frequently, “deep watering,” produces deep roots that mean lawns can better survive periods of drought. The ideal watering schedule is once or twice per week, for about 25 to 30 minutes each time.
Typical warm-season grass height range: 1-3 inches. During periods of peak growth, expect to mow the lawn once every 5-7 days. Conversely, during times of slowest growth, you'll mow less, if at all.
Once temperatures reach 77 degrees, it becomes too hot for root growth, and root growth ceases. When temperatures reach 90 degrees, it becomes too hot for shoot growth and the grasses stop growing and begin to fall dormant, with the surface grass turning a brown hue.
When long grass droops, it also traps moisture in lower areas, which can cause fungus and disease to spread. At this length, grass also looks unseemly. It may grow unevenly or turn yellow or brown.
Avoid watering grass on a hot afternoon when it's 95 degrees or higher. The best time to water grass is at dawn or in the early evening. Water deeply three times a week instead of a little water daily. Test whether your sprinkler system is watering your lawn evenly.
The resulting uneven look would be bad enough, but when you try to cut damp grass—the result is a tear rather than a clean cut. These tears open the door for fungus and moisture provides a medium for fungus to spread, so when you mow a lawn that's wet, you're creating a perfect storm for fungal infestations.
The weather is one variable landscape professionals cannot control and can make things difficult. We often get the call from some of our customers wondering why we are mowing grass in the rain. The answer is pretty simple: “BECAUSE WE HAVE TO”, not necessarily because we want to.
Q. How long should I wait to mow the grass after it rains? When dealing with mild morning dew or after light rain showers, you may only need to wait between 2 and 5 hours for the lawn to dry before mowing. With a heavier rainstorm, you should wait at least one day to mow safely.
If we struggle in this exceptional heat, then surely our grass does, too! So how long does it take for grass to come back to life after excessive heat? It can take up to 6 weeks for your grass to recover, with germination taking place between 2-3 weeks after a drought.