Turf Talk
What You Need to Know about Winter Kill By Jay McCurdy, PhD, Assistant Professor and Turfgrass Extension Specialist
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ontrary to popular belief, there are things that can be done proactively, and from hence forth, to reduce potential problems with winter kill. “Winter Kill” is a common phrase used to describe the effects of harsh winter conditions upon warm- and cool-season turfgrasses alike. Warmseason species in Mississippi and the rest of the southeast include bermuda, zoysia, St. Augustine, centipede, bahia, and carpet grasses. All are susceptible to freeze damage. But damage is not solely linked to cold weather. For instance, not all properties are equally affected. It is not atypical to see a dead lawn adjacent to a lawn that greens up well in the spring. Similarly, certain species seem to suffer more at different latitudes and due to sometimes small differences in growing conditions. There’s not much that can be done to stop the effects of cold weather, but there are some proactive strategies that help decrease the chances of winter damage.
Pro-Tips 1) Pre-season cultural practices.
The condition of grass in the spring is determined by how healthy the grass Figure 1
14 • Mississippi Turfgrass • Winter 2019
was going into winter. Proper conditions during the growing season allow turf to grow roots and store up carbohydrates needed during the winter/ spring. If turf is unhealthy due to improper cultural practices or conditions, the grass will be more susceptible to winter-injury. Mowing height. This is possibly the most important yet overlooked cultural practice. Superintendents know intuitively to raise mowing heights in the fall to allow greens to recover. That means slower ball roll, but that is cheaper than replacing greens during May and June the following season. Likewise, homeowners and other professional turf managers should increase mowing heights before cooler fall temperatures. Some possible exceptions are 1) in overseeded scenarios or 2) on high-end sports fields where athlete performance is a consideration. Perform aerification and sand-topdressing. Root health depends upon adequate soil drainage and gas exchange. There are many lawns, if not most, that would benefit from aerification to relieve compaction and promote root growth. Most golf courses try to core-aerify greens at least once per year and perform other small-tine or solidtine practices several other times per Figure 2
year. This is almost always combined with frequent and light sand topdressing. Sports field managers should at the very least be aerifying and topdressing high traffic areas, such as between the hash marks on American football fields and at goal mouths of soccer pitches. Aerification of lawns is a less common practice unless they are highly compacted. I argue that most homeowner rented aerification tools are probably inadequate to perform the type of soil disruption necessary to decrease soil bulk density and increase turf health. Timing of aerification is also critical – too early, and turf is slow to emerge from dormancy; too late, and turf health will be compromised prior to winter. Ideal aerification timing for warm season grasses is approximately May to July. This doesn’t mean you can’t vent or solid tine greens, but it does mean you need to think critically about why you’re doing these practices and whether grass can recover from the stress. Regardless of aerification, there is no substitution for proper construction of the soil medium. This means proper drainage and nutrient holding capacity. Shoddy soil construction is all too frequent in modern suburban lots and on school playing fields. Even the best Figure 3
