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Experts Provide Lawn Care Tips During Drought / Extreme Heat

What time of day should you water your lawn during extreme sun and heat?

“Irrigate early in the morning whenever possible,” Goatley said. “Irrigating during the heat of the day is considered to be very inefficient as evaporation rates are typically highest during this time of day. If it’s done at night, it increases the duration of leaf wetness which is a factor in inciting most lawn disease. If you water it in the morning, the leaves will dry more quickly. Also irrigating earlier in the day typically results in improved water distribution due to lower wind speeds at the time.”

How do you properly water your lawn?

“Watering established, mature lawns a little bit every day is not a practical approach as it enables water to remain at or near the soil surface, leaving it more prone to evaporative loss and, consequently, makes the turf’s root system not have to branch out very far to absorb the moisture that it desperately seeks,” Sandor said. “You want to set up your irrigation program to run using a deep-and-infrequent approach so that you are allowing the roots to chase a large volume of water, 0.25 to 0.50 inches, from the surface downward through the profile, going as deep in the soil as they can, using an every 3-to-4 day irrigation schedule.”

Goatley and Sandor recommend inspecting your in-ground sprinkler system and upgrading your automatic irrigation timer. There are many popular models to choose from, including novel ‘smart controllers’ that utilize real-time, local weather data to adjust irrigation programs, and many of these are available through the EPA’s WaterSense program.”

Irrigation controllers. Photo courtesy Dan Sandor for Virginia Tech.

Does watering grass in the sun burn it?

“No, standing water on a lawn can magnify the sun’s rays and can cause some yellowing or spotting of the turf,” Goatley said. “The primary problem in this situation is more likely a reduction in water-use efficiency due to evaporation of the water and/or a lack of oxygen to the turf’s roots and shoots if water is allowed to pond or puddle for an extended duration on the lawn.”

How often should you water grass during a period of extreme heat?

“The amount of irrigation required varies depending on the grass species being grown, site characteristics like the number of trees or slope of property, soil and rootzone characteristics, and your expectations,” Sandor said.

Cool-season lawns (fine fescue, Kentucky bluegrass, tall fescue, or perennial ryegrass)

“These require approximately one inch of water per week, whether from rain or supplemental irrigation, to maintain active growth during periods of drought stress. It’s extremely important if you are not going to apply supplemental irrigation consistently to maintain active growth, then refrain from applying any irrigation and stay off the lawn as much as possible.”

Warm-season lawns (bermudagrass, zoysiagrass, centipedegrass, or St. Augustinegrass)

“These will respond similarly to the irrigation, but they are much more efficient in their water use under hot and dry conditions than the cool-season grasses and do not require as much supplemental irrigation during periods of drought stress.”

Non-irrigated Kentucky bluegrass lawn during drought stress (top) and recovered lawn after accumulating one inch of rain of 13-day period (bottom). Photo courtesy Dan Sandor for Virginia Tech.

Other summer lawn care tips

  • Follow the “1/3rd rule of mowing”: Never remove more than 1/3rd of the leaf blade during a mowing event. For cool-season grasses, set your mower on its highest setting during the summer.
  • Mow warm-season grasses frequently as they are going through their most aggressive growing period of the year. They can be fertilized and aerated as needed as long as they receive enough moisture.
  • Do not fertilize a cool-season lawn as it enters summer dormancy or aerate during this drought and heat stress period.
  • Keep traffic off of the lawn as much as possible to avoid further damage to turf under extreme heat and drought.
  • Remember to dial back the irrigation timer when drought stress is alleviated and/or cooler temperatures and more frequent rainfall returns, because you do not need to water as much.
  • Patience is key!

“Remember that in the heat of summer, Fall is never terribly far away when our lawn management philosophies will change,” Goatley said. “As we begin to prepare the warm-season grass for its predictable winter-dormancy period after killing frost, your cool-season grasses have the opportunity to be rejuvenated during late summer through mid-fall.”

More information on summer lawn management. 

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