Focus : Cold Protection
Winters in Florida are generally very pleasant. Afternoon temperatures typically reach 70°F or higher, while minimum temperatures can range from 40°F to 60°F. These mild temperatures allow winter production of vegetables, citrus, strawberries, ornamental plants, ferns, and many other crops that cannot be grown in other states during this time of year. Even with its typically mild winters, however, Florida is not completely immune to frosts and freezes, and many growers must have cold protection plans in place to deal with the periodic arrival of cold air.
Several methods of cold protection are commonly used in Florida. Heaters can be used to protect high cash crops, and some citrus growers use wind machines to mix warm air aloft with cold air that has settled near the ground. Growers of low-growing crops use heat blankets to capture heat which has been stored in the ground during the day - this method works well, but the blankets must be removed quickly to avoid plant damage.
By far the most widely used method of cold protection is the application of water. Growers of ferns and strawberries use relatively large amounts of water to protect the entire plant, while citrus growers use much smaller amounts to protect only the tree trunk and scaffold limbs. When using water, growers must first determine the critical minimum temperature - the temperature at which cold air can begin to cause damage - for each crop. Then, when that temperature is reached, growers can irrigate accordingly to protect their plants.
FAWN has developed several tools to aid growers in decision-making regarding the application of water for cold protection, all of which are available free-of-charge at the FAWN website. It has been estimated that use of FAWN Cold Protection tools can save growers and water management districts billions of gallons of water and millions of dollars annually. FAWN Cold Protection tools can be used individually, or as a package in the form of the Cold Protection Toolkit, which allows users to view output from several tools following selection of a critical minimum temperature.
FAWN provides the following Cold Protection tools:
- Determining Critical Temperature - This tool gives the user advice for determining critical minimum temperature for various crops.
- Minimum Overnight Temperature - This tool can be helpful in determining whether critical minimum temperatures are possible on a given night. Read the background material to understand the limitations and rationale behind this tool.
- Wet-Bulb Based Irrigation Cutoff Tool - This tool should be used by every grower using water for cold protection. It provides the user a temperature, based on the moisture content of the air, at which irrigation systems can be safely turned off. Read more about this simple, but critical management tool.
- Forecast Tracker - This tool displays a graph that compares the NWS Point minimum temperature forecast to FAWN observations. It provides increased confidence in the forecast and can help determine the potential for freeze damage.
- Fruit Frost Station Forecasts - Allows users to view the NWS Point forecast for several of their former Fruit Frost Station locations.
- Air Temperature Threshold - A report of the total number of hours the air temperature was above or below a given user-selected threshold at any particular FAWN site.
Further developments to FAWN cold protection tools are under way, and will be published as they are completed. Incorporation of real-time FAWN and NWS data into several of the tools are examples of work that is currently being done. FAWN is also working on additional cold protection aids as we move toward providing a complete and comprehensive cold protection program for Florida growers.
Below are links to UF Electronic Data Information Source (EDIS) publications that can help you develop a better understanding of frost/freeze probabilities and how to adequately prepare for cold weather.