Winter intrusions of cold sometimes penetrate all the way south to Florida. Most vegetation in Florida is very sensitive to hard freezes and will either die back to the ground or perish completely when a hard freeze hits. It is possible to save plants in a hard freeze in Florida with a few careful preparations. Using supplemental heat is ideal to keep plants safe from a freeze, and lights are an easy-to-find and inexpensive heat source.
Light and Cover
String Christmas lights around your plants before the freeze hits. You may also place a flood or mechanics light in the center of a larger grouping of plants--you will cover these all with one cover.
Cover the plants with a blanket and weigh down the edges with bricks or other heavy materials. For plants that are taller, utilize an upside-down garbage can as a cover.
Turn the lights on before the freeze hits and leave on until the temperatures have risen above freezing. Remove the blanket during the warm daylight hours so the plants don't overheat.
Water Jug Method
Figure out how many water jugs are needed to surround each plant in a circle.
Fill the jugs with water and place around the plants the afternoon before the freeze event.
Lay a blanket over the jugs and the plants. Tuck the blanket down to the ground tight around the jugs and secure with bricks or other weights. The water jugs will have absorbed solar radiation during the day; during the night, the heat will be released from the jugs and help keep your plants warm.
Remove the blanket and jugs once the temperatures rebound above freezing the next morning.
Set up sprinklers the day before the freeze. Turn them on and adjust the spray so it hits each plant.
Water the ground thoroughly until it's moist. Turn the sprinklers off.
Turn the sprinklers back on just before the temperatures fall below freezing. Allow them to run during the entire freeze event.
Allow the sprinklers to keep running the following morning until all the ice is melted off the plants, then turn the sprinklers off.