Virginia Tech experts: Keeping a healthy lawn during extreme summer heat is possible

With little rain in the forecast, keeping a healthy lawn can be difficult but not impossible, according to turfgrass experts at Virginia Tech.

Irrigating the lawn and watering gardens is best in the morning, as the leaves will dry quickly.

“Irrigate early in the morning whenever possible,” said Mike Goatley. “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, said Goatley. “Also irrigating earlier in the day typically results in improved water distribution due to lower wind speeds at the time.”

Watering mature lawns a little every day leaves your grass more prone to evaporative loss.

“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 three- to four-day irrigation schedule,” said Dan Sandor.

Standing water on a lawn can cause yellowing or spotting of the turf.

Goatley and Sandor recommend inspecting your in-ground sprinkler system and upgrading your automatic irrigation timer.

“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,” said Goatley.

The amount of irrigation required varies depending on the grass species being grown.

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
• Refrain from applying any irrigation
• Stay off the lawn as much as possible

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

• Will respond similarly to the irrigation
• Are much more efficient in their water use under hot and dry conditions than the cool-season grasses
• Do not require as much supplemental irrigation during periods of drought stress

Summer lawn care tips

• Follow the 1/3 rule of mowing: Never remove more than 1/3 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.