Bundle your plants up against the cold

January 9, 2013 

I really upset our cats last week. I removed their favorite toy: the Christmas tree. We have two cats. Sammy is a quiet tabby cat who sits in the window seat and watches the world. The other cat is a flame-point Siamese named Finny. My daughter says Finny is “an angel from heaven,” but I think she has got her directions mixed up.

When Finny is not in trouble, he is planning trouble. He knocks things off and breaks them or chews them up. While I was taking off the ornaments from the tree and then removing the branches, I am sure Finny was thinking, “You punished me for doing that. Why are you doing it now?” I am surprised the tree survived as Finny knocked off ornaments, removed branches and chewed limbs.

Plants outside may not have to resist insane cats, but they do have to resist frosts and freezes. We can protect plants somewhat, but we cannot stop all effects of the cold. Here are some tips to help you protect plants from the cold.

There is a difference between a frost and a freeze. Frost is ice collecting on the outside of plants. Freezing temperatures are typically colder and cause ice to form inside plant cells, rupturing and destroying them. A freeze is much worse than a frost. Freezes cause internal plant damage such as split bark and damaged vascular systems. Freeze-damaged plants may bud out in the spring only to die back later because disease entered the stems through wounds made by a freeze.

Woody plants are typically resistant to freezes. They store sugars in their cells that act like antifreeze. It may take temperatures in the teens to damage woody plants. A few annual flowers such as pansies have this ability to resist freezes. Pansy flowers may die back in a freeze, (flowers are usually more tender than leaves and stems) but the plants generally recover to bloom again later.

Plants near the house or a building are usually less likely to freeze. They take advantage of the heat radiated from the building at night and the protection they get from the wind.

If you know a freeze is coming, there are things you can do ahead of time. Water the plant well two to three days before a freeze. This helps the soil to retain heat and supplies water the plant needs to prevent damage from dry, wintry winds. Mulch the plants well, applying 2-3 inches of mulch around the plant. You can apply more than this temporarily, but remove it in the spring.

Temporary covers are good plant protectors. For low-growing plants, a light application of straw can be placed over the plants to protect from frost and freezing temperatures at night, but remove this straw when temperatures warm up the next day. This is a good way to protect young vegetables or annual flowers.

Sheets or light blankets can be used as covers, but you will probably need to anchor them to the ground. Remember that plants get their heat from the ground, so anchor the cover like a tent over the plant to capture this heat. Some people put the low wattage electric lights (like Christmas lights) under the cover but be very careful to avoid shock and fire risk.

Some farmers use sprinklers to cover plants in ice to protect from frost. This is a complex tactic requiring them to monitor current temperatures, type of irrigation, etc. This tactic is not recommended for gardeners.

Snow can actually act like a cover, so it is often not as damaging as ice. Water freezing on limbs weights them down and causes them to be bend or break. There is little you can do to prevent ice damage, but covers may help some.

Our average last frost date is March 15 to 20. This date is an average. Our actual frost can be two weeks or more earlier or later. In Georgia, we tend to get a lot of our really damaging cold in late February and March. Watch the weather forecast and be prepared to protect valuable or tender plants until after the danger of a late frost is past, usually the second week of April.

Willie Chance works with the University of Georgia Center for Urban Agriculture.

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