The possibility of a hot dry summer is an ever-present hazard over most of Wyoming. You can't prevent a hot dry summer, but you can use a proverbial "ounce of prevention" to help reduce loss of valuable lawns. Waiting until there is a water shortage will be too late to start the lawn-saving steps. Instead, begin early when water is available.
Growing plants depend on the continuous movement of liquid throughout their systems. Transpiration is the moisture which is lost from the surface of the grass blades. Other problems can occur, but we will concern ourselves here with replacing water loss.
The root system continuously develops itself to replace water transpired from the leaf surface. If the necessary water is readily available near the soil surface, the plant develops a shallow root system - only 2-3 inches deep. This shallow depth means there is only a small volume of soil to hold and store water that is within reach of the roots. In addition to this, the top 3 inches of soil warms up rapidly and reaches a higher temperature. A lot of water is lost by direct evaporation from this warm soil surface and is lost to the plant.
On the other hand, grass roots at the 6-8 inch depth or even deeper would pick up moisture from a large volume of soil and water loss from evaporation would be much less.
Some species are naturally shallow-rooted, but the basic problem is developing deep-rooted lawn grass. The answer is proper watering methods. First, let us start with clearing up a wide-spread misconception that roots move toward water. Plants and plant roots have no way to move to a new location. New roots grow in soil with the proper balance of moisture and air for growth. If the balance is near the surface, roots grow near the surface; if the moisture and air relationship is better deeper down, they grow in that part of the soil.
This is the key: water your lawn down deep, then leave it for several days or a week depending on the air temperature. Let the surface layer dry out to a depth of two inches or more. This will discourage shallow root growth and roots will grow where there is more moisture. By alternately soaking your lawn to a depth of 10 inches or more and allowing the top layer to dry, your lawn grass roots develop in the important lower level.
By saturating this deep layer of soil while water is available and growing a dense root mass in that area, you are prepared to save your lawn during even a long hot dry summer. Now is also a good time to start mowing your grass a little higher. By keeping your grass at a higher level say 2 to 3 inches this will help shade the soil thus keeping it cooler and evaporating less water, but there is more leaf surface to perform photosynthesis, and by discouraging weeds from growing.
Diseases can be a problem if there is too frequent of watering or the water stands on the leaves for a period of time. So be careful when continuously watering very early in the morning and then if we have a heavy dew this could over time set up a case for disease. But it is better to water early in the morning or late in the evening versus watering during the day, when you could have a lot of the water evaporate away.
