According to the University of Florida, citrus trees do not survive cold weather without protection because they never become dormant during the winter. To avoid the cold weather, some gardeners grow their citrus trees in pots which they drag inside a heated garage for the winter, but for those whose citrus trees grow from the ground, other means of protection must be taken to keep the tree alive through the winter.
Choose a citrus variety best suited for your growing zone, based on the average temperatures. Select ornamental oranges, tangerines, grapefruit, Mandarins and kumquats for the most cold-hardy of citrus, capable of surviving temperatures down to 20 degrees F, according to the University of Arizona.
Plant your tree on a southern-facing area which receives sunlight and protection from winds.
Prepare your tree in the fall by changing your regular fertilizer to one higher in potassium (K) and phosphorous (P), with lower levels of nitrogen (N). Apply the fertilizer according to package directions.
Avoid pruning the tree during the fall to discourage new growth.
Apply an insecticide and copper-based fungicide to the tree according to package directions.
Create a bank of soil around the tree just before the first frost of the year, extending until all chance of freeze has ended in the spring. Pile soil up the sides of the trunk and covering the bottom branches.
Water the plant thoroughly before a freeze.
Only water the tree after a freeze if the soil feels dry to the touch.
Wait until new growth appears in the spring before pruning a citrus tree after a freeze, as pruning followed by another freeze can kill the plant. In spring cut off all dead branches from the tree and apply fertilizer after new growth appears.