January 2013

Last week saw some weather conditions that might cause winterkill issues for some golf courses in the area. A mid-winter thaw and substantial rainfall followed by a rapid freeze has resulted in the formation of ice sheets in lower lying parts of golf courses with poor drainage. This could be a problem for golf courses with very high annual bluegrass (Poa annua) populations. Fortunately we are, for the most part, creeping bentgrass at the Wilderness and we feel good about our chances of getting through this winter with minimal damage. That being said, we are very happy that we addressed many of the more poorly drained parts of the golf course this past fall. Please feel free to read the following article from Michigan State University in regards to winter turf injury.

Winterkill of Turfgrass  •  E0019TURF

K. W. Frank

“Winterkill” is a general term that is used to define turf loss during the winter. Winterkill can be caused by a combination of factors including crown hydration, desiccation, low temperatures, ice sheets and snow mold. Because of the unpredictability of environmental factors and differences in other factors such as surface drainage, the occurrence of winterkill on golf courses is variable and can vary greatly between golf courses and even across the same course.

Crown hydration

In general, annual bluegrass (Poa annua) greens and fairways are the most susceptible to crown hydration injury. During the warm days of late winter, annual bluegrass plants start to take up water (hydrate). Potential for injury exists when a day or two of warm daytime temperatures in late winter is followed by a rapid freeze. The most common time for winterkill associated with crown hydration and refreezing to occur is during the late winter and early spring when there is snowmelt or rainfall and then refreezing of the water that has not drained away. Crown hydration is a problem during these events because ice crystal can form in the crown of the plant, rupture the plant cells and ultimately cause the plant to die.

Annual bluegrass is more susceptible to crown hydration injury than creeping bentgrass because it emerges from dormancy and begins taking up water. Creeping bentgrass remains dormant longer and, therefore, does not take up water and is not as susceptible to crown hydration injury during the late winter.


Winter desiccation is the death of leaves or plants by drying during winter when the plant is either dormant or semidormant. Desiccation injury is usually greatest on exposed or elevated sites and areas where surface runoff is great (Beard, 1973). Winter desiccation injury to turfgrass in Michigan is normally rare, though sites similar to those described above can be prone to desiccation injury on a regular basis.

Low-temperature Kill

Low-temperature kill is caused by ice crystal formation at temperatures below 32 degrees F. Factors that affect low-temperature kill include hardiness level, freezing rate, thawing rate, number of times frozen and postthawing treatment (Beard, 1973). Soil temperature is more critical than air temperature for low-temperature kill because the crown of the plant is in the soil. It is difficult to provide absolute killing temperatures because of the numerous factors involved. Beard (1973) provided a general ranking of low-temperature hardiness for turfgrass species that were autumn-hardened.

Low-temperature hardiness Turfgrass species
Excellent Rough bluegrass
  Creeping bentgrass
Good Kentucky bluegrass
  Colonial bentgrass
Medium Annual bluegrass
  Tall fescue
  Red fescue
Poor Perennial ryegrass

Ice sheets

Ice sheets are often blamed for killing turf when, in fact, it is crown hydration and subsequent refreezing that has resulted in the kill. The reason for the confusion is that, as snow melts and refreezes, creating ice sheets, the ice sheets are often in poorly drained areas where crown hydration can occur because of the standing water. As the ice sheet melts away, the area damaged closely mirrors where the ice occurred, and therefore, the conclusion is that ice sheets caused the kill. Beard conducted research on ice sheets on three turfgrass species: Kentucky bluegrass, creeping bentgrass and annual bluegrass. Kentucky bluegrass and creeping bentgrass survived 150 days of ice cover without significant injury; annual bluegrass was killed somewhere between 75 and 90 days of ice cover (Beard, 1998). The author concluded that cause of death for the annual bluegrass was most likely from toxic gas accumulation under the ice sheet.

Snow mold

The two diseases commonly called snow mold are Typhula blight (gray snow mold) and Microdochium patch (pink snow mold). Gray snow mold requires extended periods of snow cover; pink snow mold can occur either with or without snow cover. If snow mold injury is a recurring problem, preventive fungicide applications are the best control option.

Literature Cited

Beard, J.B. 1973. Turfgrass: Science and Culture. Englewood Cliffs, N.J.: Prentice-Hall.

Beard, J.B. 1998. Winter ice cover problems? TURFAX. 9(1):1-2,5.

On another note, we have now sold all of our old golf course tee signs. I was very surprised by the interest in these signs by our patrons and hope that those of you that have them are pleased with your piece of the Wilderness Golf Course.

Another item that I would like to discuss is our greens aerification dates for 2013. We plan on closing the golf course at 1 pm on Monday May 13th to begin aerifiying greens. We will then keep the course closed all day on Tuesday May 14th and open on Wednesday May 15th. Greens will be slower than usual for a few weeks after aerifying and my hope is that people will be patient with this as the greens recover from this necessary evil.

That is about all I have to say on a very cold Tuesday morning. I wish all of you a very happy new year and hope to see you this spring on the golf course.

Vincent Dodge CGCS

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