Vast areas of turf loss is not unheard of particularly if rainfall is below normal and winds are consistent. Mounded or hilly areas tend to be the hardest hit as they will dry out sooner. These conditions are common through the Midwest, transition zone, and upper Mississippi Valley where the wind will whip across the region and protective snow cover is non-existent.
Snow acts as a blanket to help keep heat in while protecting the surface from wind-driven drought stress. Adequate drainage to improve root mass and irrigation cycles will help maintain soil moisture content during the dryer, dormant season reducing loss to desiccation.
On the other hand, direct cold temperatures are not as often responsible for turf kill. Though warm season turfgrasses, as their name states, are more adapted to warm temperatures but will go dormant during less hospitable cold stretches. In most cases, temperatures plummeting below 25 degrees F can start the process of plant mortality. Repeated or prolonged periods below that threshold can result in much more pronounced and widespread areas of winter kill.
Acclimation is the process that the plant uses which includes dehydrating cells and accumulating solutes including sugars and potassium to act as a sort of anti-freeze. This "hardening off" process is what allows the plant to withstand some cooler temperatures. Improper acclimation can lead to excess moisture in cells, freezing and rupturing cell walls.
While younger stands of turf tend to be more sensitive, certain species as a whole are less likely to withstand these conditions as well as others. St. Augustine grass, centipedegrass, seashore paspalum, and ultra-dwarf Bermuda grasses tend to be the most sensitive while common Bermuda grass and zoysia grass customarily are more tolerant.
There are some simple strategies to keep in mind for improved survival. Making sure that turf enters the winter months healthy, keeping the turf free of stress and pesky invaders, will enhance the ability of the plant to manage. Areas that are likely to stay wet or are stressed by traffic or shade are typically the ones that experience the most winter kill. Raising mowing heights and late summer applications of potassium can be a big factor in terms of plant health going into the winter. Another strategy is spring thatch management to keep the crown of the plant more protected and closer to the soil surface.
What’s more interesting is the potential for frost damage on warm season grasses in particular Bermuda grass and zoysia grass. This happens with the first hard or killing frost of the fall and can appear very random. At its best, lawns can appear mottled or even zebra- or leopard-skin like. While this looks like it should be reason for alarm, it really isn’t. Because of the finer texture of these grasses and typical tight canopies, the damage is not consistent across the lawn especially when there are variances in frost formation.
The last bit of potential damage occurs when the turf tries to break dormancy too early. Grasses that start to green-up prior to milder conditions face the potential for wild swings of cooler weather resulting in burn of sensitive new growth. As mentioned by Dr. Fred Yelverton of NC State on Twitter, premature green-up followed by low temperatures particularly those that persist can easily result in damage. He calls it the 3-strike rule which can end up being fewer strikes if cold temperatures persist.
The extent of winter kill or this spring damage will be evident as those areas will fail to green-up. Be prepared for some plugging if necessary and hopefully it won’t be vast areas of sod. Keep weeds in check and monitor for insect or disease pressure while establishing new turf.
Reach out to the Ewing Technical Services Team with questions, or if you have topics you would like us to discuss.