The weather this week is going to be interesting. The National Weather Service is forecasting a couple of nights in the lower to middle 20s for the middle part of the week and the cold weather will be back on Saturday. The drought monitor that was released last Thursday (January 11, 2024) indicates no drought conditions for South Georgia.
Below are a few words from Dr. Clint Walz, UGA Turfgrass Specialist, about the cold weather and warm season lawns.
As this new year begins, weather continues to be weather with impending cold conditions in January – imagine! Within the 7-day forecast the prediction is for air temperatures to range from the low-twenties to low-teens from middle Georgia to the piedmont. With spring 2023 still fresh on the minds of turfgrass professionals where warm-season grasses were slow to grow, questions have arisen as the possible impact of the upcoming “cold snap”. Within biological systems there are few “absolutes” but considering the recent environmental conditions, I foresee a minimal likelihood of damage to turfgrass from this system alone. The warm-season grasses have been dormant for over two months (first frost event for this season in Griffin was November 2, 2023) and frost has been observed 6 of the first 10 days this year (i.e. January), with several being “heavy” frosts. Corresponding, 4-inch soil temperatures have ranged in the mid-40’s. These have been ideal conditions for dormancy – the cessation of growth due to internal and external factors. Cold injury to turfgrass is generally associated with cold and dry conditions. While the late fall and early winter were dry”ish”, recent rainfall has been plentiful for keeping the growth points of the grass plant hydrated. So, do turfgrass managers and homeowners need to do anything to prepare lawns for a January cold snap? Simply stated “No”. There are things not to do, however. Do not “freeze”, or irrigate, your lawn. For some crops (e.g. strawberries) short-term freeze events can be mitigated by encapsulating the plant in ice. That may sound counterintuitive, but water freezing is an exothermic (gives off heat) process. For it to work, irrigation must be continuous until air temperatures rise above freezing. This time of year, warm-season grasses do not have green tissue, or fruit, to preserve with this technique. Additionally, the excess water can do more harm to the turfgrass root system by saturating the soil. This applies to cool-season grasses, like tall fescue, as well. Lastly, there is no need to fertilize for the forecast conditions. Currently, there is minimal biological activity in warm- and cool-season grasses with low nutrient uptake. Applying any fertilizer now has a greater likelihood of leaching beyond the root system than being taken up by the plant. Why spend money on nutrients the plant will not use? Unlike last year, the air and 4-inch soil temperatures this January have been cool and not stimulated a premature green-up. Grasses are fully dormant and resilient enough to handle some cold weather.
Ornamentals and Seasonal Color: Dr. Bodie Pennisi, University of Georgia Vincent J. Dooley Professor
Cold weather is once again upon us. While there’s not much we could do to prevent it from happening, there are things we can do to minimize potential damage to ornamentals in the landscape.
Plants become acclimated by gradual decreases in temperature over a period of time. Often we see more damage after a period of warm weather, followed by sudden freeze. Most plant parts can adapt to cold, but fruits and roots do not develop good cold tolerance. With proper plant selection and siting, much of the damage from cold can be averted. Tree canopy and structures offer protection. New plantings should have a good layer of mulch to serve as an insulation.
Watering landscape plants before a freeze can help as well. Wet soil will absorb more heat during the day and radiate it during the night. If below freezing temperatures are expected, having more moisture in the soil is beneficial; as water freezes, it releases heat. This works only as long as there is liquid water – once it’s all frozen, the temperature will drop below freezing. Plants in containers, in particular are more prone to damage. Containerized plants should be moved to protected areas where heat can be supplied or trapped. If they can’t be moved, placing them closer together and covering with mulch will reduce heat lost from the container walls. Coverings protect more from frost than from extreme cold. The most effective covers are those that extend to the ground and do not touch the canopy. Setting holiday lights under the cover is an easy method to raise the temperature around the plant.
After a freeze, assess damage but do not prune too soon. Brown leaves can be removed right away but you should wait to do any strong pruning until new growth appears. This way you can be sure you are not removing any live wood and reducing stored reserved even further. Often cold injury is not as obvious, and extent of damage is evident weeks or months later. For woody plants, brown/black cambium layer under the bark and lack of spring bud break and/or an overall weak appearance, is a clear indication of damage.
Much can be learned by anticipating where potential problems can occur and when. In the 2023 winter, we saw considerable damage to many shrubs and even trees. And while by mid-summer many did recover, not all have. Indian hawthorn even some crape myrtles that were pruned too hard are either dead or most of the aboveground is not active. Those more damaged plants, have entered winter with lower reserves, and are more sensitive to freezing weather than the rest. Make a note of these weakened plants and re-assess in late spring. Most likely, replacing will be necessary. Additional information can be found here: Effects of Low Temperatures on Plants
Have a safe week and stay warm!!
Jeremy M. Kichler
Colquitt County Agent
The University of Georgia Cooperative Extension does not endorse or guarantee the performance of any products mentioned in this update.
