MSU Extension Gardening in Michigan

Summer Lawn Care 

Prepared by: Bob Bricault MSU Extension Educator

Michigan lawns are commonly a mix of Kentucky bluegrass, creeping red fescue and perennial ryegrass. Sodded turf is usually a blend of varieties of Kentucky bluegrass. These grasses are cool-season grasses — they grow best in spring and also in late summer to early fall when days are warm and nights are cool. Spring and fall are times of growth for blades and roots of grass plants and the development of new plants. Simple cultural practices through the summer can aid the grass in surviving the stresses of summer.

Watering lawns in summer

Cool-season turf grasses often require supplemental watering in the summer to remain green and actively growing. During hot and dry periods, the turf needs light, frequent watering that add up to 1/2 inch to 1 1/2 inches of water per week. Grass roots are naturally shorter during hot, dry conditions of summer, and applying too much water at that time can waste water because it simply moves past the root zone of the plants. The best time of the day for watering is morning to early afternoon. Avoid watering in the evening — this extends the time that lawns remain wet through the night, and that can encourage fungus diseases. If summer watering restrictions are in place that ban daytime watering, then apply water to turf between midnight and daybreak.

Dormant lawns in summer

Growth of cool-season grass slows as summer weather becomes hot and dry. Lawns not watered during extended dry conditions will go into a dormant state and grass becomes brown. Dormancy is a protective mechanism allowing a lawn to survive during unfavorably dry conditions. During an extended drought of 3 to 4 weeks along with temperatures in the mid-80s or higher, dormant grasses continue to lose moisture from the crowns of the plants. Continued loss of water in the crown can cause the plants to die. To prevent death of dormant plants, apply about 1/2 inch of water every 2 to 3 weeks. This amount will not green up the lawn but provides enough moisture to keep plants alive until temperatures begin to cool and rain becomes more consistent. Fine-leaved fescues include hard fescue, creeping red fescue and Chewings fescue. Sheep fescue is a fine fescue that has excellent drought tolerance but is more suitable for areas mown only once or twice per year.

Fertilizing lawns in summer

Because growth of grass slows or stops during the summer heat, fertilization in the summer should be limited to times of water availability. A dormant lawn is not actively growing, so fertilization should wait until it comes out of dormancy. For lawns that are watered and remain green and continue to grow, summer fertilization can be beneficial. Usually summer fertilizers are applied at low rates to match the slow growth that naturally occurs. Fertilizers labeled for summer turf application reflect this reduced rate with lower spreader settings listed on the bag. This may amount to 25 percent to 50 percent less nitrogen used per application.

Late summer (late August to early September) is a good time to fertilize the lawn as nights become cooler and rainfall usually occurs more frequently. Nutrients supplied at this time are available to the grass plants as they enter an active period of growth.

Grubs in turf

Grubs are a common problem in many lawns during the summer. Turf damage is caused by the feeding of grubs (immature stage) of European chafers and Japanese beetles. Both these beetles emerge from the soil and begin to lay their eggs into turf in late June. Eggs begin to hatch in early July, and young grubs begin to feed on the grass roots. Control measures used at the time of egg hatch can be effective as a preventive measure. (For an overview of products and their effectiveness and correct timing, visit the MSU Turfgrass Science Web page at www.turf.msu.edu/grub-control-2012/.)

Keep in mind that cultural practices can reduce the impact of grubs. Lawns watered through the summer can survive grub infestations better than unwatered turf. The simple task of raising the mowing height to 3.5 inches encourages a larger root mass that is less affected by grub activity.

Mowing

Mowing turf is a crucial management practice that can lead to stressed lawns if not done correctly. Keep your lawn mower blade sharp to cut grass blades cleanly without ripping and shredding the tissue. Grass blades not cut cleanly are more prone to water loss. Summer mowing height is important to reduce plant stress. A mowing height up around 3 inches or more shades the soil and reduces evaporation, reduces weed seed germination (especially crabgrass), and provides more leaf surface to capture light and produce sugars used for healthy plant growth. Cut as often as needed to remove one third of the growth at a time. Leave grass clippings in the turf to break down and return nutrients to the turf.

References

Cregg, B. May 2010. Everything is obvious once somebody shows you…Washington State University Extension: The Garden Professors. Available at https://sharepoint.cahnrs.wsu.edu/blogs/urbanhort/ archive/2010/05/03/everything-is-obvious-once-somebodyshows-you%E2%80%A6.aspx.

Davis, T., and Smitley, D.R. 2012. Home Lawn Grub Control Products 2012. Michigan State University Turfgrass Science. Available at http://turf.msu.edu/grub-control-2012/.

Frank, K.W., and Lyman, G.T. 2004-2010. Irrigation Practices to Preserve Water Quality. Michigan State University Turfgrass Science. Available at http://turf.msu.edu/irrigationpractices-to-preserve-water-quality