With their evergreen leaves, fragrant flowers and delicious fruit, citrus, such as oranges, lemons, grapefruits and lines, are favorite landscape trees in the Citrus Belt, stretching from California along the Gulf Coast to Florida. Yet even in these warm climates (USDA Zones 8 to 10), the weather gets cold enough two or three times each winter for frost to threaten these tender plants. Follow these steps to avoid frost damage.
1. Water and Remove Mulch
When a freeze is predicted, check to see if the soil around your citrus is damp or needs watering; trees that are water-stressed will freeze more quickly. Moist soil will also absorb and hold heat from the sun more effectively than dry soil. Removing mulch from the base of the tree, either temporarily or for the entire winter, will expose the soil to the sun so it can radiate heat back to the plant at night.
2. Construct a Shelter
Covering citrus—especially young plants—with a shelter during very cold weather helps slow down heat loss, often enough to save the tree. To build simple covering, drive four strong stakes into the ground around the tree. The tops of the stakes should reach above the canopy of leaves. Connect the tops of the posts with horizontal supports. then lay plastic or burlap over the supports and stakes, covering both the top and the sides. Fasten the material to the stakes with thumbtacks or staples so it won't blow away. it's important to make sure the material does not touch the leaves because this will cause them to freeze.
3. Add Additional Heat
You can use electric lights to raise the temperature inside the shelter by two to four degrees F. A safe way to do this is to place on or two trouble lights on the ground within the shelter. Be sure to plug the lights into an extension cord or outlet intended for outdoor use.
To prevent the buildup of excess heat in the shelter during the day, remove the top and roll up the sides during sunny weather. Replace in late afternoon if there is another threat of frost. When the cold spell is over, you can remove the stakes or leave them in readiness for future needs.