As temperatures are dropping in North Georgia, you may be concerned about your early budding plants. Last week we were seeing temperatures in the 70s and things beginning to bloom. It was certainly starting to feel like Spring, however we were snapped back to Winter with lows in the 30s this week. Last year, our blueberries took a hit with a late frost in April. This year, we are trying new ways to protect against the frost.
To protect against frost we are misting our plants in the early evening, when temperatures begin to go down, and then before the freeze (prepare for a little science lesson). It may sound counterintuitive, as you think when water freezes it continues to get colder. But actually, when water freezes it stays at a constant temperature.
If a cup of water was 55 degrees F and placed outside where it was 20 F, the water would cool to 32 F and then stop cooling. It would then turn to ice. Once it is completely frozen, the temperature would continue to decrease. Liquid water has more energy than solid water, this energy is released when it turns from a liquid to a solid. This release of energy is called latent energy. When the energy was released, heat was also being released. While this heat was released, it prevented the temperature of the water from going below 32 F.
So, when you mist your plants before a frost comes, it slows down the plant from going below freezing. It is important to note that this is not a good strategy if the temperatures are going below 25 F, or an extended period of days below freezing temperatures, as it will continue to cool down (causing more harm to the plant). For us in North Georgia this is perfect, as temperatures during late winter and early spring average around 34 F in the early mornings, and in the 50s during the day.
We used this strategy for our blueberries. For our other greens, we covered them with cloth blankets. If plants are potted, you could also bring inside for the night.
We hope this protects your plants from the low temps for lots of delicious food to be enjoyed this summer!