Summer months bring warm temperatures and sometimes periods of dry weather to the lawns of Northern Illinois. Grass lawns across Antioch-Gurnee-Waukegan and Lake Forest enter survival mode to withstand the stress associated with this time of year. Even after a great spring of cool temperatures and excess rain made lawns green and grow fast, they are quickly turning to mid-summer appearance of splotchy brown and dormant patches in just a few short hot days this summer. Proper mowing height and watering practices are two of the most important things to do properly as summer begins.
With the forecast of multiple 90 degree days ahead and no significant rain in well over a week, begin watering now to prevent or assist with heat stress on the lawn. A bluegrass-based lawn needs about 1-2 inches of irrigation per week to keep adequate moisture levels and to prevent the full onset of browning and dormancy. Although this amount of irrigation is adequate for moisture needs it doesn't always keep a lawn from going dormant, but it does give it the best chance to maintain some green during heat stress. Soil temperatures will cause the stress and irrigation will help but not eliminate this on hot sunny days.
Remember we have cool season grasses that thrive between 60 and 80 degree soil temperatures and 1-2 inches of irrigation weekly. Right now we are seeing soil temps in the 130’s in sunny areas and no rain at all. Shade areas stay green as they are only as warm as air temperatures in the upper 80's.
Some lawns are greener than others even though they are under similar conditions, but there are reasons why. Lawns are made up of several different grass types and some are more reactive to higher temperatures than others. Fescue grasses stay greener longer into heat and drought stress compared to bluegrass. Bluegrass is probably the most sensitive to higher temps as the leaf blades actually fold up like a sail making it look much thinner and weaker compared to other grasses. Lawns are also made up of different consistencies of clay, gravel sand, etc. The more clay the soil has, the more it radiates the heat back into the grass unlike thick layers of rich topsoil. This is the biggest cause of “spots” as areas of the lawn contain various amounts of clay, sand etc. underneath causing some of the spots.
Along with watering regularly during hot and dry summer months the lawn should also be mowed properly. Less frequent and at a taller height will keep activity on the grass to a minimum and allow for full shading of the soil below with longer leaf tissue. Also be sure that when you do mow the lawn, never remove more than a third of the leaf tissue height or else additional stress and moisture removal will be unnecessarily added to the lawn that is already stressed out. Keep in mind, lawns will return to their beautiful green and thick appearance as soon as cooler and rain returns to the forecast, usually in late August.