All across the internet there are different ideas and opinions about ways to protect trees from a freeze. I’ve listed out every method I know and the pros/cons of each, including, blankets, sprinklers, buckets of water, incandescent or Christmas lights, drip lines, propane, hay, fertilization, tree canopies, etc.
Protect Trees with Blankets
This is the most basic form of protection during a freeze, the equivalent of putting a sweater on yourself to keep warm
Pros: Can be made cheaply from old clothes(good will) sewn together, easy to set up for small to medium trees.
Cons: Storage space of large blankets, not effective when windy, complexity increases with the size of the tree, cost if you purchase the blankets new, only offers a few degrees of protection.
Sprinklers
This is the common method of protecting large crops of citrus in florida. It works on the principle that it takes a lot of energy to change water from liquid to ice. During that transition, the water will stay at 32 degrees even if the air temperature is far below that.
Pros-Very easy if there is already an irrigation system and very good protection
Cons-Cost of water, damage can be severe if the water stops before the air temperature rises above freezing, must have an overhead irrigation system.
Hot Water Bucket
Used in conjunction with blankets or plastic sheeting, a 5 gallon bucket of hot water is placed under the tree. The hot evaporating water keeps the plant warm for about 2-3 hours and the blanket helps keep the heat in.
Pros-High heat capacity of water keeps plant warm for an extended period of time, easy to do with a small number of plants.
Cons- Not possible if you have more than a few plants, must change the water every few hours.
Protect Trees with Christmas Lights
This is the primary method I use to protect trees on my property from any kind of freeze. I splice several outlets into an extension cord laid out to each plant. This allows me to have one extension cord service 3 to 4 plants. Each plant gets 1 to 2 sets of christmas lights (you could use 40 watt light bulbs) and then wrapped in plastic.
Pros – Looks pretty, raises the temperature under the plastic by about 10 degrees even on windy nights, incandescent lights can be purchased very cheaply after Christmas for about $1 per set per plant.
Cons – adding too many lights can burn the plant, Must use incandescent lights (led & cfl don’t produce enough heat), if you don’t turn off the lights and remove the plastic during the day, you will kill the tree because trees cannot breath through plastic.
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