Citrus trees are among the most popular types of fruit trees that home gardeners include in their landscaping. Lemons, limes, oranges, tangerines and other citrus fruits contain Vitamin C, calcium and other important nutrients. But if you live and garden north of USDA Plant Hardiness Zone 8, your citrus trees run the risk of frost damage when the temperature dips below 20 degrees F. Use one of several methods to winterize citrus trees and protect them from cold damage.
String Christmas lights over and around your tree. The warmth these lights provides can be sufficient to protect trees from light frosts, according to Four Winds Growers. Turn these lights on at night when the weather forecast predicts frost or temperatures below 32 degrees F for your area. You can also hang a 100-watt light bulb in the center of your tree, according to the University of California.
Turn on a yard sprinkler that will cover your tree with water on nights when the temperature is forecast to drop below 32 degrees F. Because running water cannot freeze, it will protect your tree from frost. Although this method uses a large amount of water, it can save your tree.
Spray an anti-transpirant over your tree in fall, before the first hard frost occurs. The University of California at Davis reports, "anti-transpirants are chemicals capable of reducing the transpiration rate when applied to plant foliage." When plants are exposed to cold temperatures, they lose water. An anti-transpirant helps your citrus tree to retain its valuable juices.
Build a frost frame by constructing a box from 2-by-2-foot boards that is tall enough and wide enough to cover your citrus tree. Drape clear plastic over the top of the frame and around the sides, stapling it in place.
Move your tree indoors for the winter, if possible. If you grow your citrus tree in a large container, move it indoors for the winter before the first frost occurs. Provide six to eight hours of direct sunlight each day, or install fluorescent grow lights above your plant. Maintain a minimum temperature of 50 degrees F at night---warmer temperatures during the daytime will also benefit the tree. Reduce your watering of citrus trees that you bring indoors over winter as it is their dormant season.