Warm-season grasses such as hybrid bermudagrass and zoysiagrass are commonly used on fairways in the transition zone. These grasses offer many benefits in this part of the country when compared to the cool-season alternatives – reduced water use, lower pesticide requirements and greater stress tolerance during the primary playing season are a few of their greatest attributes. Even though turf breeding efforts have resulted in several cold-tolerant varieties, warm-season grasses are still susceptible to injury during periods of extreme winter conditions. Unfortunately, for the second time in three years, many courses in the central U.S. are now dealing with the lingering effects of extreme winter weather on warm-season turf and the damage has been extensive in some cases.
Many superintendents attribute the injury to a rapid decline in temperatures in late December. Temperatures dipped to the low single digits, or even lower, for three consecutive days. Many areas also saw windy conditions and didn’t have snow cover to insulate the turf or protect it from desiccation injury. To make matters worse, conditions leading up to the extreme cold were relatively mild, which didn’t allow the turf to harden off and prepare for the cold as well is it could have. Conditions prior to cold weather are just one of several factors that impact the severity of winter injury, which is why some courses were affected more severely than others. Other factors that impact turf’s susceptibility to winter injury include:
- Shade
- Soil texture
- Orientation to the sun
- Soil moisture
- Maturity of turf
- Traffic
- Snow cover
- Wind exposure
When it comes to the timeline for recovery, it is worth noting that warm-season grasses require warmer conditions for aggressive growth and recovery than cool-season turf. A good rule of thumb is the “150 Rule,” meaning that for warm-season grasses to grow well, the sum of the high and low temperatures for the day must reach 150 or greater. Unfortunately, most areas affected by winter injury have also seen unseasonably cool conditions this spring. For example, Tulsa, Okla., has only seen six days where the “150 Rule” has been met this season. Warmer weather is coming, but until then, patience is necessary. You cannot fertilize your way out of cool temperatures.
Turf breeding efforts have resulted in several varieties of cold-tolerant warm-season grasses that offer many benefits in the transition zone when compared to cool-season alternatives. These grasses have superior cold tolerance when compared to older warm-season varieties and should be strongly considered in areas with hot summers and the potential for extreme winter weather. However, we must remember that all warm-season grasses, improved or not, have a vulnerability to winter injury. In addition to grass selection, it is important to evaluate the other factors that impact turf’s susceptibility to winter injury to reduce risk in the future. Contact your regional USGA agronomist if you would like help developing plans to mitigate the risk of winter injury, or to develop a recovery plan if damage has already occurred.
Central Region Agronomists:
Zach Nicoludis, regional director – znicoludis@usga.org
Paul Jacobs, agronomist – pjacobs@usga.org