Keeping Plants and Trees Warm When Temperatures Drop

李武军

This is the VOA Special English Agriculture Report.

Florida, in the southeastern United States, is called the Sunshine State. It grows more oranges than anyplace except Brazil. But Arctic air has damaged some Florida oranges and strawberries in recent days, and killed fish at tropical fish farms.

The unusually long period of cold weather has shown how even warm climates can sometimes freeze over. But protecting plants and trees in the garden may not be too difficult if you follow a few suggestions.

Ice protects these oranges during an overnight freeze last week in Apopka, Florida

Sudden cold can be the biggest threat, especially after a warm period. Plants have not had a chance to harden their defenses. Those that are actively growing or flowering are at high risk.

Try to choose plants that live best with cold weather, and planting areas that face west and south. Being near other growth may also provide warmth.

Most frost damage takes place at night. Ice crystals form on the leaf surface. They pull moisture from the leaves and keep plant tissues from getting water.

Cold weather is most likely to damage or kill plants that do not have enough moisture. So keep the garden watered. Moist soil absorbs more heat than loose, dry soil covered with mulch or vegetation.

University of Arizona extension experts say covering plants and small trees with cloth or paper can help prevent frost damage. A one-hundred watt light bulb designed for outdoor use can also provide warmth. Some people place Christmas lights on young trees for warmth. The bulbs should hang below the leaves to let the heat rise into the tree.

Cold is especially dangerous to citrus trees. Agricultural specialists at the University of California suggest putting paper or cloth around the trunk and central branches of young citrus trees.

In Florida, as temperatures fell to record lows, citrus growers sprayed water on their trees to help prevent freeze damage.

Jim Bottcher is a master gardener with the University of Florida extension. He explains that as the water freezes, it produces heat, and the ice forms a protective blanket around the tree. If you spray a tree, keep the water away from nearby power lines. Heavy ice can form and break them.  

You can also wrap a tree in palm tree frond leaves, cornstalks or fiberglass. Adding plastic film works well in rain and snow. But experts say plastic alone does not help much.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. More gardening and agricultural advice is at 51voa.com. I'm Bob Doughty.