Citrus trees do not experience a full dormant period, which means they can be injured by cold temperatures in winter. Some varieties of citrus have greater cold tolerance, but all need protection from winter frosts. The best defense is a good offense, but if you forgot to protect your citrus tree against winter frost, there are some steps to take to save your tree.
Leave your frost-damaged citrus tree alone until the spring, when the danger of frost has passed for your area. Do not fertilize the citrus tree during this period, either.
Look the tree over for signs of frost damage in the spring. Frost-damaged leaves will be hard and brittle. Severely damaged leaves can fall off the tree. Frost-damaged bark can seem somewhat loose from the tree. The tree may also develop oozing cankers.
Cut away a frost-damaged limb using anvil pruners or lopping shears. Rather than cutting off only dead wood, make this cut in living (and healthy looking) wood. Cut branches back to the intersection with the trunk or to the crotch intersection with another limb.
Remove all frost-damaged areas and wait to see how the tree grows. Damaged-areas can continue to die months after the freeze. Observe the tree for signs of growth after you've pruned.
Water the citrus tree lightly when you see signs of new growth, watering until the soil is moist, but not saturated.
Apply fertilizer when the tree resumes spring growth. Use the same type of fertilizer that you normally use, but offer the tree half the amount of fertilizer. The University of Florida recommends more frequent and lighter applications of fertilizer for frost-damaged citrus trees.
Slowly increase the watering until you are offering your tree the regular amount water.