It has been a tough winter! I won’t rehash all the details as we have all suffered through it, other than to say we have had more than double our average annual snowfall, and it has been very cold. Sprinkle in a couple of warm-ups, and some rain, and that makes for some interesting turfgrass scenarios heading into Spring.
Winterkill is a broad term used to encompass many types of turfgrass death during the winter period. This can be broken down into several categories including ice damage, crown hydration, snow mold damage, and desiccation. Throughout the Midwest and Northeast, these issues will be encountered by many golf course superintendents. I would like to take a moment to discuss each of these and then address the potential impacts on our golf course.
Desiccation by definition simply means “to dry thoroughly; dry up”. During the winter months, turfgrass loses its ability to take up moisture as it does during the growing season. With prolonged exposure to winter wind, it can become dehydrated with no ability to recover those water losses. Long enough exposure then can result in the death of the plant. In past years this is something we have watched closely as our site has little cover to buffer constant winds. But this winter, this has not been a concern as we have had constant snow cover for the vast majority of the winter.
|Example of winter desiccation of a bentgrass putting green|
Snow mold damage can occur from two different pathogens that thrive in certain types of winter conditions. Pink snow mold, or Microdochium nivale, is a fungal pathogen that can form with or without snow cover, and thrives in a temperature range from 30-60 degrees Fahrenheit. Gray snow mold, Typhula species, is a fungal pathogen that requires extended snow cover for development. Both of these are of concern this season, but preventative plant protectant applications were made in late Fall to minimize this risk. These applications are not fool proof and do have a limited life span as the plant metabolizes the product, but I do not expect widespread turf loss due to snow mold.
|Gray snow mold|
The next two types of winterkill are of particular concern this winter. Ice damage has already been reported at golf courses throughout the region. Ice has been present on turf surfaces since late January. Damage from ice accumulation is not completely understood, but the belief is that when dense, nonporous ice presents itself, toxic gas accumulations can eventually cause turf loss. The timeframe that grass can survive under ice has not been well researched, but it is generally accepted that after 45 days for Poa annua, and 90 days for creeping bentgrass, managers should be aware of the potential. Superintendents who manage Poa annua greens have had concerns for some time now as they have passed that 45 day threshold. Steps have been taken to remove snow and ice as well as evacuate water from greens surfaces, some successful, some not. Bentgrass managers, while concerned, aren’t quite on edge just yet. On our site, I would prefer to maintain the layer of snow insulation and wait for a big melt to come as we still have some time yet before we approach the 90 day threshold.
|Ice damage to a putting green|
Crown hydration injury is something we will be monitoring over the next few weeks as the snow begins to melt. The crown of the plant is where all growth initiates. During the winter months, if a thaw presents itself and temperatures rise to a point where a plant may begin to break dormancy, it can then begin to take in water. If this is followed by a rapid freeze, this water can then turn to ice and cause the plant cells to rupture, causing death. Again, Poa annua managers find this much more concerning than bentgrass managers, as Poa tends to break dormancy much earlier than bentgrass. To date, we have had one warmup where this may be a concern, but moving forward during late winter and early spring, this will continue to be monitored.
As noted earlier, this has been a very difficult winter. There likely will be turf loss discussed at many courses throughout the Midwest and Northeast. Comparisons from course to course are not advised as many issues can affect winterkill, from local climates to microclimates, trees, wind movement, snowfall amounts, topography, practices implemented, and even budgets and labor availability. We are fortunate to have bentgrass as our primary species on our greens, tees, and fairways. Bentgrass has a much greater tolerance to the stresses of winter. With a little luck, hopefully some of the minor Poa annua spots we do have will succumb to the winter difficulties. And I would never say there won’t be some bentgrass turf loss. But I do believe we have implemented to best practices to put us in a position to minimize the risks presented.
As for when we will resume play, on greens specifically, I know that is what many of you really want to know. That is up to Mother Nature. First we need to melt the snow, and while it doesn’t seem like it will happen, it will eventually. Then we need the surfaces to firm up. As the ground begins to thaw, it will thaw from the top while frost will remain several inches below. Should we allow traffic during these conditions, we have strong potential to cause lasting damage to the putting surfaces as it would be like walking on water balloons. Traffic could cause significant rutting and root shearing which would last well into the summer before full recovery. I believe the potential exists that we may be well into April before we can safely utilize the greens. I hope I am being overly pessimistic as I want to get out there as much as you do. I will update further as information presents itself.
Click here to view the Winter Turfgrass Update from the Chicago District Golf Association