Winter brings a host of challenges to those who maintain athletic fields. Yes, there can be problems for those sports turf managers who just have to keep their turfgrass healthy until warm-weather activities start again. But the situation is much more complex for field managers whose facilities are being used through at least part of the winter. And for much of the country, this means dealing with low temperatures and winter precipitation.
What can you expect when winter arrives? Certainly, personal experience or the shared experiences of others is a common source of information. I recommend looking at climate data and recorded weather happenings from the past. That will give you an idea of what might happen.
For more northern locations, the obvious first step is to select a turfgrass variety that’s compatible with colder weather. If in winter use, it should also be resistant to wear. This is especially important since growth rates will be reduced due to lower temperatures and less sunlight, thus regeneration of the grass will be slower to occur.
A major concern of all turf managers is to prevent winterkill, an all-inclusive term referring to turf loss in winter due to a variety or combination of causes. Crown hydration injury occurs when internal water in the crown freezes, causing cellular damage and death. Cool-season grasses are especially susceptible to this since they’ll break dormancy with the first occurrence of warmer temperatures and start absorbing water. A return to below-freezing temperatures will produce damage. Rapid temperature changes are particularly bad. On the other hand, a lack of water can lead to desiccation, which can also cause injury or even plant death. This can be a problem in winter, as the cold air is even drier. If precipitation is frozen, the water contained in it won’t be available to plants until melting occurs.
Extreme cold can produce other problems. Soil temperatures may fall to a point where damage is done to the below-surface part of the turfgrass plant. Another problematic scenario occurs if the melt water refreezes into an ice sheet. The ice covering may prohibit gaseous exchange between the turfgrass and outside air, causing damage or death. Additionally, snow mold can strike fields during winter. Some types are specifically associated with snow cover, others are not.
For an idea of what type of temperatures you’ll be facing, check the National Weather Service for your area forecast. Expected daytime high and nighttime low temperatures will be given, typically with a high degree of accuracy.
Although not as bad as some of the conditions noted above, frost can also produce some damage to turf. It’s not the frost itself – which is just visible ice crystals on the outside of the grass leaf – that causes problems. If there’s any type of traffic on frost-covered turfgrass, mechanical damage can happen when ice crystals are driven into plant tissue. Damage is superficial and typically repairs itself.
In most regions, frost can occur in the spring and again in the fall, ending the growing season. In southernmost areas, frost can occur occasionally in winter. The NWS will send out either a:
- frost advisory if local surface temperatures may reach freezing;
- freeze warning if widespread below freezing temperatures are expected;
- hard freeze warning if temperatures at or below 28 degrees Fahrenheit are predicted.
There are numerous advantages to keeping a field covered and sports turf managers have a wide variety of covers, turf blankets, etc. to choose from. Protection of turfgrass prevents winterkill. Although the air can get very cold in winter, the ground cools slowly and is typically warmer than the air in winter. A cover will hold the heat in, thus protecting the grass. How much covering you’ll require depends on the actual low temperatures expected. Darker colored covers will absorb radiant energy from sunlight and help warm the grass below them. A cover will also protect against desiccation.
In terms of the turfgrass itself, snow isn’t a problem. In fact, a snow cover acts as an insulator and will keep the grass and ground below it just near freezing despite how cold the air above it may get.
If it’s economically worthwhile to do so, there are technological devices to combat some of these winter problems. Subsoil heating systems will mitigate the effects of cold temperatures and melt freezing or frozen precipitation. Specialized and supplemental lighting systems can make up for the lack of real sunlight.
For athletic fields that are in use, winter precipitation, which can occur well into the South, is another major concern. Keep track of the latest forecast. The NWS has a number of specific products dealing with winter precipitation:
- a winter storm warning is a general advisory for winter precipitation;
- a heavy snow warning indicates significant snowfall for an area (this varies with location, less in the South);
- a freezing rain advisory or ice storm warning indicates icing conditions of some degree.
If it’s a game day situation and precipitation is forecasted, keep an eye on weather radar. Most times, precipitation will move into an area and not form over top of it. With radar, you can watch the moving area of precipitation and from that determine if and when it will reach you.
If snow does occur, then snow removal becomes a major issue. Snowfall amounts are very difficult to forecast. There can be tremendous variation over small distances. Besides the amount, the type of snow can also affect removal procedures. Most field managers prefer to use snow blowers to minimize potential damage to the turfgrass. These work best with dry snow, typical with colder temperatures. But when temperatures are close to freezing, the snow can be very heavy and wet. Careful plowing may be the only alternative. Of course, an obvious advantage of covering a field is to keep precipitation from affecting the playing surface. A cover will keep a field dry and aid in snow removal.
Some of the most challenging situations occur when unusual weather occurs, even if it is predicted. In particular, extreme cold or winter precipitation occurring in the southern states. Field managers may not have the tools to deal with these situations. But outside help is often available.
And we can’t forget about the crews who maintain the field. The effects of cold temperatures are magnified by the wind. Wind will literally blow heat away from your body and it will cool much quicker than under calm conditions. Extremities are most vulnerable, especially if exposed. The often-used wind chill factor combines the actual temperature with the wind speed to give an “effective temperature,” one the body will feel. It’s a much better measure of the danger of the cold.