It’s been some number of years since we have had more than minimal reason to have concern about turf injury that can occur as a result of severe winter weather. This year’s intermittent periods of brutally cold temperatures, accompanied by significant winds, and less than adequate snow cover providing some aspect of insulation, gives cause to review some previous presentations about “winterkill” potential and a wide range of factors involved. We widely refer to several USGA articles in this presentation.

Winterkill is an easy problem to define but difficult to fully understand. Simply put, winterkill occurs when turf dies during winter. However, understanding the mechanisms that cause winterkill, creating effective prevention strategies and formulating effective recovery programs is complex.

What causes winterkill? Winterkill is a catch-all term describing winter injury to turfgrass that occurs through a variety of mechanisms such as ice suffocation, crown hydration, low-temperature injury and desiccation. Identifying the exact cause of winterkill is difficult because winterkill may be caused by one mechanism or could result from a combination of mechanisms that act simultaneously or occur at multiple times during winter. Additionally, turfgrass species have different tolerances to winter injury. For example, creeping bentgrass is much less susceptible to winter injury than Poa annua or ryegrass, two species for which we have small percentages here at WCC.

Can winterkill be prevented? A silver bullet that prevents winterkill has not been found. However, great strides have been made breeding turf varieties that have a better tolerance of winterkill mechanisms. For example, USGA-funded research has resulted in the release of cold-hardy Bermuda grasses varieties such as Patriot that do appear to have improved, but not assured, cold tolerance mechanisms. In as much as this variety composes much of our practice tees, this winter will prove to be a telling test.

Golf course superintendents are not able to prevent winterkill, but they can implement a variety of programs that give turfgrass playing surfaces the best chance of surviving winter. Common strategies north of the Mason-Dixon line include converting to cold-tolerant turf varieties, implementing proper fall fertilization, raising mowing heights during fall, reducing shade, and improving drainage. All are actively pursued in our overall maintenance programs.

What are the most effective recovery programs? Winterkill damage can range from minor to severe, and golf course superintendents use a variety of methods to repair the damage. Weak areas of turf may recover with fertilization and traffic restrictions, but dead areas must be re-established with seed or sod. Repairing an area that has been severely damaged by winterkill is an opportunity to make improvements that may help avoid future damage. Correcting shade, drainage or traffic issues will improve turf conditions during the golf season and winter hardiness. Re-establishing a severely damaged area also provides an opportunity to use cold-tolerant turf varieties that will be less vulnerable to winterkill in the future.

Winterkill is a seasonal visitor that no golf course wants to see. It often arrives quickly, but the impact on playing conditions can last for weeks or months. Golfers can take comfort in the knowledge that golf course superintendents and scientists are working hard to understand and overcome the age-old problem of winterkill and with your continued support, concerns and damage realities will continue to diminish. Now we just need a little cooperation from Mother Nature to limit the severity and/or duration of our winter season.

Dan Pierson
Director of Grounds