A hard freeze is considered 28 degrees for 4 hours or more. To be completely safe, protect young trees (under 5 years) whenever temperatures drop below 32 degrees. Be sure you take extra precaution by covering the area where the rootstock and scion were joined. Water the plant 48 hours prior to the freeze. If you tree is healthy and has been watered and fertilized properly, it should be able to survive here in North Florida.
Protecting citrus from cold temperatures is important for current and especially future crops Citrus can grow in most parts of the state, but most types require protection when cold weather rolls in. Cold protection is achieved by trapping ground heat. While covering the entire tree is best, if your tree is too large, wrap the trunk with several layers of cloth. It is particularly important to protect the area where the scion was grafted onto the root stock. Either way, make sure the covering reaches all the way to the ground and is secured. Remember to remove it when the temperature returns to above freezing. Newly pruned trees are much more susceptible to cold damage, so postpone pruning until spring. In North Florida, choose cold-hardy citrus varieties or keep the plants in containers so they can be moved to a protected area. With a little care, your tree can come through cold weather.