Freezing temperatures, plus snow and ice, sometimes lead homeowners to wonder whether their lawn will make it through the winter unharmed. Although there’s often little to fear if the lawn is a cool-season grass (such as fescue, bluegrass or a fescue/blue mix), the question is certainly more relevant if the lawn is surfaced with a warm-season grass (i.e., bermudagrass, zoysiagrass, St. Augustinegrass or centipedegrass).
Winterkill of warm-season grass can occur in several ways. Sometimes, rapid or sustained drops in temperature below 23°F can cause deadly tissue damage. Other times — for instance, during a temporary early spring thaw with significant moisture in the soil — the turfgrass crown (the part just at the top of the surface) can absorb more water than usual. If freezing weather returns, ice crystals can form within the turf’s cell walls, causing them to burst and kill the tissues. Alternately, a lethal combination of low humidity, windy conditions and drought or frozen soil moisture can result in desiccation (“drying out”) of the grass. Finally, traffic on frozen or slushy turf can also cause substantial damage.
If you suspect that your lawn may have suffered from winterkill, you can diagnose the problem long before the grass is expected to green back up in spring. Simply bring in some plugs (3” wide by at least 3” deep) of the grass from suspicious areas, and plant them in containers (labeled with the specific lawn areas) with native soil and drainage holes. Place the pots near a southern-facing windowsill in a warm room, and keep them adequately watered. Within two to three weeks, assess how much live green tissue has appeared. Plugs with less than 50% greening are indicative of extensive damage and may mean that those areas of the lawn will need to renovated or replaced. You can continue doing this type of sampling throughout the winter and early spring as cold temperatures persist.
Another way to determine winterkill damage is to inspect the plant crowns outside. If they have collapsed and the plant tissue is black or brown, the grass has been damaged.
Areas of the lawn most likely to suffer winterkill or damage are those that are on north-facing slopes, heavily shaded, poorly drained or grassed with poorly adapted cultivars (such as older cultivars of bermudagrass).
If major areas of your lawn end up damaged from cold weather, consider replacing the entire lawn with a more cold-tolerant variety — either a cool-season grass or a warm-season variety such as Patriot bermudagrass, Meyer zoysiagrass, Raleigh St. Augustinegrass or TifBlair centipedegrass (all available from Buy Sod).