During 2007, most areas in the southeastern United States set records – unfortunately, those records were for high temperatures and lack of rainfall.
The lack of overall soil moisture, combined with low temperatures and desiccating winds, often results in extensive damage or “winterkill” to the Bermudagrass. This occurs on turfgrass plants that are unprotected from wind and have limited soil moisture due to either drought conditions or low temperatures (frozen soil moisture). When temperatures rise above 32 degrees F (0 degrees C), turfgrass leaves lose water to the atmosphere due to pressure created from the low humidity conditions. Consequently, turfgrasses dry out, causing desiccation of plant tissues and important plant proteins.
Diagnosing low-temperature injury
Superintendents should anticipate certain areas of turfgrass which may be more susceptible to low-temperature injury than other areas. Cultural factors contributing to low-temperature injury and increased susceptibility include poor drainage, soil compaction, excessive thatch, reduced light intensity (shade), north or northeastern facing slopes, excessive fall nitrogen fertilization, and low mowing heights. If any of the aforementioned conditions are present, or have occurred, and low-temperature injury is suspected, utilize the following methods to determine the severity of the potential damage.
1. Collect turfgrass plugs using a cup cutter from suspected low-temperature damage areas.
2. Place or plant these plugs in a suitable container of native soil with drainage holes, properly labeling them.
3. Place the containers in a greenhouse, or in a room beneath a heat lamp or grow light, or as a last resort, in a southern facing window.
4. Keep the turfgrass plugs adequately watered.
5. Note that turfgrass should initiate growth and greening within 7 to 10 days.
6. Assess the amount of greening after plugs have been grown for two to three weeks. Suspected areas with less than 50 percent greening should be considered extensively damaged from low-temperature exposure and will probably require renovation. Lesser damaged areas may recover with proper management practices and extra attention.
7. Repeat the above sampling procedure on a 14- to 21-day interval through the periods of potential cold weather injury.
Renovation steps
If renovation is required, steps to consider include the following:
- Variety: Determine which variety of turfgrass to establish during the renovation process and contract with your preferred turfgrass supplier for a quantity of grass to complete the renovation process, visit the turfgrass farm, and select and/or approve the turfgrass selected.
- Equipment: Ascertain the equipment and financial requirements needed to complete the renovation process and budget accordingly. Advise membership of the upcoming conditions and necessary renovation steps.
- Plan: Strategically plan your fertilization and herbicide programs to promote optimum grow-in conditions for the renovated turfgrass. Fertility should be based on soil sample recommendations to provide a well-balanced growth response between turfgrass roots and leaves. DO NOT apply a root-inhibiting preemergence herbicide during the renovation process. Use one containing oxadiazon (e.g., Ronstar herbicide) which has minimum negative impact on rooting.
Bert McCarty is a professor of turfgrass science at Clemson University.