Should I be watering my lawn in the evening? There's this one reason this could be causing issues for your grass

Sizzling grills, ice cubes clinking in a glass - forget all that, the sound that tells me summer is really here is the hiss of sprinkler doing its thing to keep lawns looking green and healthy. For my neighbors, it's always an early evening activity – a period on the end of a day spent enjoying their outdoor spaces. 

But is this actually the best time of day to water a lawn? There are a few solid rules to keeping a lawn healthy, especially when you're looking at how to grow grass in hot weather, and alongside when to mow and how often to water, when you water is one of them, too. 

So, should you water your lawn in the evening? I asked lawn experts to settle the debate. 

When is the best time to water your lawn? 

All the experts I asked agreed that watering your lawn is a task best performed in the morning. 'The best time to water a lawn is between 4am to 9am because you’re allowing time for the grass to absorb the moisture, ensuring that the water reaches the roots more effectively and does not just evaporate,' explains professional landscaper Scott Gilmore, owner of Landscape Creations.

Jeremy Yamaguchi, the CEO of Lawn Love, agrees. 'When deciding when to water your lawn, simply follow “the earlier the better” rule. The perfect time typically happens to be early in the morning sometime before 10am. The temperatures are lower and calm breezes ensure least evaporation. So, the water gets soaked into the soil and absorbed by the grass roots in a more effective manner.'

So, what about watering a lawn in the evening?

If you miss the opportunity to water your backyard in the morning, doing it in the early evening is still an option, say experts, especially in warmer weather. 'If that time is not possible, the next best time to water your lawn is usually late afternoon somewhere between 4pm-6pm,' Jeremy says. 'Again, the winds are calmer during this time and the absorption level is good enough.'

However, this window is tight for a reason, and for some experts, they simply wouldn't risk watering a lawn at this time of day. 'Watering your lawn in the evening is something I wouldn’t recommend,' Scott tells me, 'as it will leave the grass blades wet overnight.' 

So what's the problem with a wet lawn during the evening? 'Watering in the late evening or overnight will encourage fungal diseases as infection incidence increases when grass leaves stay wet for extended periods of time,' explains Matthew Koch, Ph.D., Director of the Genetics, Biotech, Lawn Nutrition, and Seed Teams at ScottsMiracle-Gro. 

(Image credit: Kate Wichlinski. Design: Richardson & Associates Landscape Architecture)

Is there any time I shouldn't water my lawn at all?

Aside from late evening or overnight, it's also not advisable to water your lawn in the middle of the day, especially when it's warm out, but it's possibly not for the reason you think. The idea that watering your lawn in direct sun can cause 'scorch' is a bit of an old wives' tale, but it's simply not the optimum time for your lawn to receive water. 

'Avoid watering during the middle of the day to stop the lawn losing too much water to evaporation especially during the warmer months,' Matthew explains.