The heat of summer is upon us and along with it comes a number of lawn issues that are dealt with differently than in spring and fall. First, watering. The two most important guidelines to remember are 1. Water to the bottom of the roots and 2. Keep the roots moist, not soggy or dry. Regarding #1, it’s helpful to know how deep they are, so dig a little to find out. Also, with the increasing heat, they naturally shrink in depth. For example, Kentucky bluegrass roots may be 6-8 inches deep in the spring, and 2 inches deep in June, July and August. Watering beyond the depth of the roots is wasteful, while shallow watering causes even more shrinkage, as the bottom parts of the roots dry out.
A common old husband’s or wive’s tale is that watering the lawn (sometimes called syringing or spritzing) for 5-10 minutes during the heat of the day to “cool it down” is helpful in summer. Not so. UNL research indicates that the effect is only good for 5-10 minutes. Much like misting houseplants, once the water vapor stops being applied, the influence of the heat of the sun starts right back up. Fortunately, Mother Nature made turfgrass plants with a built in system for cooling themselves called transpiration. If you water to the bottom of the roots and keep the roots moist, you’re watering correctly and helping the turf to survive summer’s weather conditions. All that is accomplished with syringing is the waste of water during the heat of the day through evaporation.
If watering is done with this in mind, a light fertilization will help the turf withstand summer heat stress. Be sure to use a “summerizer” fertilizer, with a 1-0-1 ratio of the nutrients – nitrogen, phosphorous and potassium. The potassium benefits the turf by encouraging stress tolerance and the nitrogen provides for steady leaf growth. The little known fact about nitrogen is that it also helps with root growth, which is super important in summer; the more roots the better. Generally, a light to moderate application is called for, using about a third to a half of the bag.
While mowing, you’ve no doubt seen broadleaf weeds such as clover, dandelions and plantain in the lawn, and have been tempted to try to control them with herbicides. Not a good idea. First, these plants usually develop an extra thick waxy layer in the heat as an adaptive mechanism and tend to repel applied herbicides. Second, application of herbicides in summer is always risky as the heat and wind can cause them to drift or vaporize to desirable trees, shrubs and veggies and cause them to be damaged. Mid fall applications are much more effective and safe for landscape plants.