Turfgrass tips for surviving summer

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

I don’t think anyone knows what a typical summer weather pattern in Michigan really means anymore, but if there’s anything that can be guaranteed it’s that the weather will be unpredictable. No doubt there will be hot spells, dry spells, downpours, and at some point we’ll wonder if it’s ever going to rain again. So how do you help prepare the turf for the wild ride it’s about to enter?

Fertilization

Avoid heavy nitrogen fertilizer applications as summer gets rolling. Typically, the Memorial Day weekend is the trigger for making a fertilizer application that will help the turf grow throughout the summer months. Search for fertilizers that have some slow release nitrogen in their analysis. Look for terms such as slow release, slow acting, delayed release or natural organic. All of these terms will indicate that the nitrogen will be released at a slower rate than a water soluble nitrogen source such as urea. High nitrogen fertilization applications using water soluble nitrogen sources at this time of year will likely favor top-growth over root growth and won’t help the turf through the summer stress period.

Irrigation

Based on personal observations, I have concluded that the majority of home lawns in Michigan are not irrigated. There are certain neighborhoods in every city that have many homes that have in-ground irrigation systems where the lawns are irrigated throughout the summer, but overall most people let Mother Nature take care of their irrigation needs.

If you’re not concerned about having a green lawn and rains are lacking, the turf will turn a lovely shade of brown and enter dormancy. Dormancy can be thought of as the turf in a resting state, it will turn brown and cease growing, but will remain viable and resume growth when moisture becomes available. The cool season turfgrasses in Michigan can typically survive from five to eight weeks under dry conditions before substantial death occurs. Even if you choose not to irrigate throughout the summer, if the weather turns hot and there is no rain for five to six weeks, I would recommend applying between 0.5 and 1.0 inch of water to ensure turf survival. This is what I call a “mercy irrigation.”

If you desire a green lawn throughout the summer, there are two irrigation schemes that can be followed. The first is the traditional irrigation schedule of deep and infrequent applications in order to discourage shallow turfgrass rooting, flush salts from the soil profile and reduce weed competition. For those without in-ground irrigation systems, this is most likely the irrigation schedule you’ll follow. Apply between 0.5 to 1.0 inches of water weekly, depending on precipitation and temperature. Depending on your soil type, applying this amount of water at one time may be feasible or may lead to lakes in your back yard. If you have a clay soil, split this application up over several intervals during the day or over a couple days.

If you choose to irrigate your lawn to maintain a green, actively growing turf you need to consider many factors to devise a scheme that works for your lawn. Is the lawn shady or sunny; is the soil type clay or sand; is the turfgrass Kentucky bluegrass or tall fescue; does your community have watering restrictions? All of these factors need to be considered before mapping out your strategy. Here at MSU, we’ve been advocating for several years now to think outside the box and apply irrigation on a more frequent basis than the typically recommended weekly Saturday morning soaking of 1-1.5 inches of water. The light, frequent application scheme has proven to provide excellent quality turf. However, as mentioned above, in some areas irrigating every day may not be allowed by law, so in that case you obviously need to do some tweaking. In those situations, consider watering every other day or maybe every third day – you’ll have to experiment with amounts applied.

What about timing? Generally, avoid irrigating in the early evening hours as this results in the turf remaining moist, damp, and subject to disease activity over the entire night time. If possible, irrigate in the early morning hours. We have also seen benefit from doing very light irrigation (0.1 inch or less) applications during the early afternoon to reduce heat stress. This is particularly effective when trying to alleviate the symptoms associated with the disease necrotic ring spot.
I don’t believe there is one simple irrigation recommendation that is going to work for everyone’s lawn. The key to irrigating successfully is to understand the site, measure your expectations and recognize your limitations, whether it’s watering restrictions or maybe the lack of an irrigation system.

Mowing and heat tracks

Make sure to stay on top of your mowing this spring to avoid scalping the turf and thereby stressing the turf. Mow at the high end of the optimal mowing height range for the turf. For Kentucky bluegrass, mow at 3 inches. Higher mowing heights will help the turf develop a deeper root system. Every summer you can see damage from mowers or vehicles driving through drought or heat stressed turf. (view photo) The damage occurs when the turf is close to wilting or suffering from heat stress. In June 2006, I observed wide spread heat track damage on landscape turf throughout many areas of suburban Detroit. The only sure fire way to avoid heat track damage would be to keep all equipment off the turf during heat or drought stress periods, especially between the hours of 11:00 AM and 2:00 PM. Of course, this is a huge problem for large mowing operations that operate from early morning to evening. If you can’t avoid mowing during this time, apply a light dose of irrigation to cool the turf prior to any mowing.

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