By Waldo Terrell
Temperatures in the southeast, as well as the rest of the country, have been cold enough to have turf managers worried, and rightfully so. The information below illustrates the growth characteristics of warm-season turfgrasses:
Warm Season Grasses
- 120°F : Shoot growth ceases.
- 110°F: Root growth ceases.
- 80-90°F: Optimum shoot growth.
- 75-85°F: Optimum root growth.
- 74°F: Optimum time to overseed bermudagrass with ryegrass in the fall. Time to plant grasses in the spring.
- 64°F: Expected spring root decline is triggered and roots turn brown and die within 1 or 2 days.
- 50°F: Root growth begins to slow below this temperature.
- 50°F: Chilling injury resulting in discoloration is possible.
- 50°F: Initiation of dormancy occurs resulting in discoloration.
- 25°F: Low temperature kill possible.
The last line provides reason for worry. Temperatures have been colder this January than I can ever remember them in 36 years of living in the southeast. Dr. Jeff Higgins wrote a blog last year about winter kill and how to respond to it.
After taking those steps, there is no guarantee you won’t have winter injury. For that reason I would recommend re-evaluating your pre-emergence program. If you’ve used a pre-emergence herbicide that adversely affects rooting I would recommend switching to a different chemistry, like Ronstar, that doesn’t affect turfgrass rooting. More information can be found in our pre-emergent herbicide selection article from 2010.