Freezing temperatures and Florida isn't a connection many of us immediately make. However, temperatures below 32°F can have a significant impact on the this state's orange crop. Lows this winter have fallen into the 20s and snow has been reported as far south as the Florida Panhandle. To help combat the effects of freezing temperatures, farmers spray their crop with water to protect it when temperatures drop below freezing.
Morning Temperatures in Mid January
There are no hard and fast rules to determine when a plant will freeze; there are a wide variety of factors that can affect both the temperature at which a plant will freeze and how extensive the damage will be. Some of these factors include the minimum temperature observed, the length of time at the minimum temperature, how well conditioned and old the plant is, and the health of the tree. For smaller branches, temperatures of 28°F and lower for four consecutive hours can kill them. Larger branches and trees can typically withstand 12 hours of temperatures below 28°F.
So, how exactly does spraying water on the orange crop protect it from freezes? As the water freezes on the plant, latent heat is released. If sufficient water is applied, more heat is added to the crop than is lost as a result of evaporation. This heat allows the temperature of the plant to remain at the freezing point as long as the ice coating remains. Some articles state that this can keep the temperature of the oranges 2-4°F warmer. This method works for temperatures as low as 24°F. When temperatures drop below 24°F, more damage could be caused than if the plants weren't sprayed. Also, if winds are higher than ten mph, spraying the plants may offer little to no protection.
Ice on Oranges in Florida
The effects of a freeze on Florida citrus extend well beyond the Sunshine State. Over three-quarters of the country's orange crop is grown in Florida. They also produce approximately 40% of the orange juice supply worldwide. The loss in the orange crop reaches far beyond Florida and can be felt in our pocketbooks at the supermarket.