December Dilemma

By Bob Vavrek, senior agronomist, North Central Region
December 15, 2011

The temperature at ground level beneath a standard woven cover can reach the low 80’s on a sunny day when air temperatures barely climb into the mid 40’s.  No doubt this can disrupt the natural hardening process of turfgrass during fall and the de-hardening process during late winter and early spring. 


A few more courses try to protect greens with covers every time a region is affected by a severe bout of winterkill.  Unfortunately, conditions for winter injury from ice suffocation and crown hydration have been quite favorable these past several seasons, so the number of courses trying covers for the first time has increased dramatically.

The top ‘frequently asked questions’ with respect to green covers for the first time user is the issue of timing.  Superintendents that have little or no experience with covers want to know the optimal time to install and remove the protection.  Experienced superintendents know this is a crapshoot. 

Why worry?  First, installing a cover too early may delay or reverse the turf hardening process.  Temperatures will increase quickly under a cover during a few consecutive days of mild, sunny December weather, and this may encourage the turf to break dormancy.  Similarly, mild weather during late winter can encourage early green-up and turf growth beneath a cover.  This could make the turf susceptible to low temperature injury once the covers are removed.  

The standard rule of thumb regarding covers is to install the material as late as possible before the first significant snowfall and then remove the covers early in spring.   Some courses try to acclimatize greens to increasing spring temperatures by removing the covers during the day and replacing the covers during the evening if the night temperatures are predicted to plummet.  Obviously, this requires a lightweight cover and an appropriate amount of labor at a time when staffing will likely be limited. 

Several courses in southern Wisconsin installed covers during mid-to-late November in anticipation of cold temperatures and snow.  No snow cover and mild weather has made several superintendents second guess this decision; even more so when they see green grass under the cover and little, if any, frost in the soil.  Their question is: Do I remove the cover and try to allow the turf to harden off before the really cold weather arrives?  The answer would be simple if we could predict the weather with any more probability than a coin toss. 

Yes, removing the cover and exposing the turf to several consecutive days of temperatures in the 40’s and nights in the high 20’s to low 30’s would benefit the grass with respect to cold tolerance.  Yes, removing the cover may also expose the grass to cold temperature injury and crown hydration (much more likely in mid-December versus mid-November).  Yes, you might remove covers for a couple of days and then have no way to quickly replace and anchor covers back into frozen turf just ahead of the next snowstorm.  Weather plays a big part in what you can or cannot, should or should not do when the decision is made to use green covers.  Is it any wonder that covers tend to provide the most consistent benefits when they are used in the northern reaches of the region where once it gets cold, it stays cold and where consistent snow cover is the rule, not the exception. 

No doubt, the recent mild weather presents a December dilemma for those who covered greens early.  Hopefully, Santa can provide everyone healthy turf and plenty of happy golfers next spring regardless of whether covers are used or not.

Merry Christmas and a Happy New Year to all

Source:  Bob Vavrek, or 262-797-8743 


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