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Back Yard Gardener: Drought-stressed lawns

Hello Mid-Ohio Valley farmers and gardeners! We welcome the first week of October as we end one of the hottest and driest Septembers on record. I believe fall is coming starting this weekend so we can enjoy outdoor activities without the heat and humidity. As our heat loving summer vegetable such as tomatoes and sweetcorn finish up I hope many of you plant a cover crop on your garden. Winter wheat, rye as well as legumes such as hairy vetch and clover are seeded to keep the soil covered this winter as well as building organic matter.

As dry conditions persist in the Valley homeowners are asking if they should regularly water the grass in the lawn or let it be. Of course the easy answer to remedy drought stress on lawns is to apply water. Deep, infrequent watering to the depth of the root system is an ideal situation. However, this should be done when lawns show the first signs of drought stress,

During a dry spell, many lawns will show initial symptoms of drought stress. As the grass loses water, its leaves become less rigid and begins to wilt. You can see footprints remaining after walking across the lawn because the grass stays flat after it is stepped on rather than “bouncing back.”

The most obvious symptom of drought stress are crunchy tan or brown leaves of grass that have entered dormancy. This helps the plant conserve water to stay alive and survive a drought. Drought stress is most noticeable on slopes in the lawn established on poor soil or shallow top soil.

This dry spell has not only sent Kentucky bluegrass into dormancy but even tough and hardy turf type fescues. As late as we are in the growing season, if your lawn has gone dormant I would not try to irrigate. Once cool-season turf grasses have gone dormant by stopping active growth and turning off-color it’s best to leave them in that condition rather than watering heavily to cause the grass to green-up again.

Breaking dormancy actually drains root reserves within the plant, and if conditions remain dry and the weather is hot, the plant is not likely to replace those reserves. In a normal summer, lawns may go dormant and resume active growth when conditions improve. The downside of dormancy is the appearance of the lawn and the risk of problems arising on an inactive lawn such as opportunistic weeds sprouting.

Many homeowners want to know how much water is enough to keep the turf alive. In order to keep your lawn green during hot and dry periods, at least one inch of water will need to be applied weekly. That can be expensive as well as using quite a bit of water for an extended dry period. Another option for drought is to water with one-quarter to one-half inch of water once every two to four weeks once the turf goes dormant. This amount of water will not green up the turf, but it will increase long-term survival of the lawn during long dry spells by keeping plant crowns hydrated.

Stay off the lawn with the mower, even if we receive some rains and the grass starts growing again. Mowers and other heavy equipment can cause substantial damage to vulnerable, stressed grass. Whenever possible, limit traffic of any type on the lawn. Once rains return, the turf will begin to recover and grow new leaves within two weeks but the clock is ticking on our growing season which will end with the first frost and cold weather.

During normal conditions, as a general rule keep mowing heights at least three inches for most turf stands. Lawns mowed at higher heights tend to have deeper roots, less weed problems, and look much better. Mowing too close invites problems such as weed invasions. As always, mowing should be on a frequent basis so that no more than one-third of the leaf blade is removed in any one cutting. Taller turf allows more shading of the soil, conserving what moisture is in the soil.

Avoid applying excess nitrogen fertilizer during hot, dry conditions. Lawn grasses will respond by putting out excessive growth when they should be going dormant. Drought stress will occur faster on turf stands with poor soil conditions underneath. Soil compaction, clay fill, low pH, and general poor conditions for root growth will become very evident under stress conditions such as drought. Contact me at the Wood County WVU Extension Office 304-424-1960 or e-mail me at jj.barrett@mail.wvu.edu with questions. Good Luck and Happy Gardening!

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