Lawn damage might seem trivial compared to drought’s impact on agriculture, but lawns do have a role in human and environmental health. They reduce atmospheric carbon dioxide while releasing oxygen, filter pollutants that would end up in rivers and streams, and naturally cool the surrounding air by 7 to 14 degrees, according to University of Minnesota.
At this point of the region’s drought, most lawn owners have already decided whether or not to water their lawns, or just wait for rain. For those who have opted to continue watering, lawns need about 1 inch of moisture per week to remain green and growing.
For those who have chosen not to water their lawn, we’re lucky because Kentucky bluegrass, which is the region’s predominant lawn grass, has the ability to go dormant when soil is dry. Dormancy is a self-preservation mode, in which grass hunkers down and stops growing. Although the leaf blades turn brown, the crowns, rhizomes and roots remain alive, ready to resume growth when favorable moisture and temperatures return.
Dormancy has its limits, though, and there’s a point of no return, as some of us discovered in the drought of the late 1980s when some lawns died. Dormant lawns can’t go indefinitely without water, and occasional moisture is needed to keep the crown and roots hydrated and alive.
To keep dormant grass crowns and roots alive, some moisture is needed every three to four weeks. Michael Vosburg / Forum Photo Editor
How much moisture is needed to keep dormant grass alive? According to University of Nebraska, one-fourth of an inch of water every three to four weeks will help ensure hydration and viability of crowns, rhizomes and roots, either from scattered rain showers or by irrigating. The grass won’t turn green, and its dormancy won’t be broken, but it will stay alive.
Keeping a dormant lawn at least minimally hydrated will greatly increase survival and speed the green-up once adequate rainfall resumes. How much moisture does it take to pull a lawn out of dormancy and get it to turn green and pleasant? The exact amount depends on soil type, but it takes considerable water and cooler temperatures to return grass to pre-drought beauty, because the subsoil below has become so depleted during drought conditions. Generous water will be needed to replenish moisture in the root zone.
If we can keep our lawns at least alive, they have the ability to self-repair thin spots once moisture conditions improve. Kentucky bluegrass spreads by underground rhizomes, which lets it fill bare, patchy spots created by extended drought. Thin areas up to 6 inches in diameter can quickly fill in as the bluegrass moves laterally. Larger blank areas might require reseeding. If fall moisture is adequate, fertilizing in early September will help the grass recover.
- Adjust expectations and focus on keeping the lawn alive, and not necessarily lush.
- Early morning irrigation is best, as it maximizes efficiency and reduces potential for disease.
- Maintain a high mowing height of 3 inches. Turfgrass maintained at higher mowing heights has a deeper root system able to access water at greater depths. Taller turf shades the root system.
- Mow in the evening or early morning during hot weather to reduce likelihood of damage.
- Keep lawn mower blades sharp. Using a dull mower blade causes jagged wounds in the leaf blades, causing grass to lose 30-50% more water.
- Allow clippings to filter into the lawn instead of bagging.
- Delay fertilizing and herbicide applications until September, when the summer heat has passed.
- Reduce traffic on the lawn. Foot traffic, heavy lawn mowers and vehicle tires can cause serious injury to brittle, drought-stressed grass.
- If you’ve opted to let your grass go dormant, the lawn still needs a quarter inch of water every three to four weeks, either from rain or irrigation, to remain alive and hydrated.
- If you’ve opted to continue watering your lawn, irrigate deeply to develop a deep healthy root system. Frequent light sprinklings cause shallow roots. Apply 1 inch of water once per week in one application on clay soils. On sandy soil, split the watering into two applications.
Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at email@example.com.