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Turfgrass Science

Protecting Bermudagrass Entering Winter

Gregg Munshaw

University of Kentucky

It was about this time last year that I started hearing rumors that we were going to have a really cold winter. Well, the bad news is that I am hearing the same thing again. Although the Washington Post cautions that no one can really be sure what a winter will be like this far in advance, there is still the possibility of another tough one. So, if we have another cold winter, what did we learn from last winter?

1. Kill was widespread; wet areas, low areas, high areas, north facing slopes, high traffic areas, etc; we saw dead bermudagrass in all of these places.

2. The only way to guarantee you do not get bermudagrass winterkill is to not grow bermudagrass.

Because we cannot guarantee we will not lose grass on any given winter, there are a few things that have been shown to be effective in reducing the incidence of winterkill.

Potassium fertilization. If your soil test shows that the K level is anything less than adequate, fall K fertilization can help reduce winterkill. However, if the soil already has adequate K levels, adding more fertilizer will not help.

Nitrogen fertilization. The traditional approach to N was to stop fertilizing in late August. Research over the past decade has shown that N does not contribute to winterkill. Nitrogen will keep bermudagrass green and recovering slightly longer into the fall, but it will also encourage winter weeds.

PGRs. Plant growth regulators have been shown to improve carbohydrate storage in late summer early fall. In theory, improved carbohydrate levels should result in increased winter survival.

Mowing heights. Some believe that raising the mowing height during the fall will give crowns/stolons/rhizomes a little more insulation against cold. It is also thought that the taller plants will improve carbohydrate status. This is one area where I cannot agree or disagree with the practice and could not find any data to support or debunk this theory. However, if raising mowing heights doesn't affect playability or appearance, why not try it in the event that it actually does help.

Overseeding. Very little work has been done on how overseeding affects winter survival. We do know that there is only a slight increase in temperature at the soil surface with overseeding, but not enough to likely make a big difference; kind of like raising the mowing height.

Covers. This one is fairly obvious. Covers have been used to successfully reduce bermudagrass winterkill for many years. The largest problem with covering a field is the cost of the cover. An alternative to purchasing a cover is to annually cover the turf with wheat straw. This method is also effective at reducing winterkill, but can be a chore to remove in the spring.

Topdressing. Heavy topdressings have been used for many years to help moderate surface temperatures. Soils are excellent buffers of temperature and can moderate the temperature around the crowns very well. The problem once again lies in spring cleanup. If a fairway/athletic field is topdressed, it likely will not be a problem. However, when putting greens are heavily topdressed, it can take some time to work the sand into the canopy.