Winterkill of Turfgrass in Michigan
Michigan Turfgrass Winterkill
You’ve done everything you need to do throughout the year to keep your lawn in the best shape you can. You’ve cared for it, fertilized it, trimmed it — yet after the long, cold winter you notice bare brown spots when the snow melts. Could it be winterkill?
What is Winterkill?
Winterkill is the term we use for any type of brown or “dead” spot that is left after the snow melts. It covers a large range of woes that are caused my many different factors. These factors include damage due to crown hydration, desiccation, low temperatures and snow mold. In addition to environmental and weather variations, more localized differences exist, such as a drainage. Lawns seem to have a lot going against them in the winter. This is why it is so important to keep them healthy throughout the year. Contact Fit Turf and schedule an evaluation to learn how we can help keep winterkill at bay.
Crown Hydration Winterkill
During the days of late winter, injury can be sustained by lawns when a day or two of warmer weather during the daytime is followed by a rapid freeze at night. During this time, ice crystals form in the crown of the plant that rupture the plant cells, ultimately causing the plant to die. According to Michigan State University Extension, this type of winterkill occurs more so in annual bluegrass species than in creeping bentgrass: creeping bentgrass remains dormant longer than do annual bluegrass types. Therefore, it doesn’t take up water and is not as susceptible to crown hydration injury in the late winter. Although ice sheets are often blamed for causing turfgrass winterkill, it is most often likely crown hydration and subsequent refreezing.
Lawns that are covered with snow can survive a wide range of temperature fluctuations. Think of the snow as a blanket, insulating what’s below. Desiccation can occur when very cold temperatures are met with bare, uncovered dormant or semi-dormant grasses. Uncovered grasses continue to lose oxygen and moisture, and the frozen roots cannot replace the moisture lost. This results in cell death. According to MSU Extension, this type of injury is most likely on elevated sites and areas where the runoff is greater.
At temperatures below 32 degrees Fahrenheit, ice crystals can form and cause what is known as “low-temperature kill.” This is where the type of grass you have chosen for your lawn comes into play. Hardiness in turfgrass species varies widely: from excellent to poor. Some turfgrass species that MSU’s Extension considers “Excellent” to “Good” include rough bluegrass, creeping bentgrass, Kentucky bluegrass and colonial bentgrass. “Medium” to “Poor” low-temperature hardiness species include annual bluegrass, tall fescue, red fescue and perennial ryegrass.
Another cause of winterkill is snow mold. There are two types of snow mold: Typhula blight, known as “gray snow mold” and Microdochium patch, or “pink snow mold.” Gray snow mold requires snow cover that lasts for extended periods, whereas pink snow mold can occur either with or without snow cover. Snow mold is a fungal infection that is characterized by fuzzy or crusty patches on portions of the lawn. Improving air circulation in turfgrass helps improve this situation, which can be achieved by regular dethatching and aeration. Additionally, an application of a preventative fungicide is helpful.
Reestablishing Turfgrass After Winterkill
If damage has occurred, it may be necessary to either reseed or resod your lawn to facilitate recovery. This may include stripping the dead turf and sodding the area. Fit Turf can help provide you with some guidance after winterkill. Give us a call for a free evaluation. We can provide you with recommendations based on your grass type.