By Mike Isbell
University of Georgia
I'm surprised the creeping gardenias at my house have made it through the cold. Truly frigid weather (12 degrees at my house) is supposed to severely injure them. I knew that when I planted them, but it's been so long since we've had a real winter I just didn't think we'd see temperatures like that.
Years ago -- OK, many years ago, back when we had "real" winters and I was a kid at home in north Georgia, and back when it seemed to snow every year, and we saved water in big pots because the water pipes froze all the time, and I slept in an unheated room and no electric blanket -- now, that was cold.
At night, even with so many blankets and quilts I could hardly turn over in the bed, the only way to stay warm was to sleep rolled up in a ball. I didn't dare stretch out, because those sheets at the foot of the bed were ice cold.
We didn't worryBack then, we didn't worry about outdoor plants freezing. We worried about the water freezing and pipes bursting. And we didn't worry too much about Spot and Butch, our old "sooner" dogs freezing. You do know what a "sooner" is, don't you? You know --"sooner one breed or another."
Now we worry about our plants freezing. So if you're worried that cold weather may cause the demise of your plants, here's what you can do.
Bring in your containerized plants. But remember, even an unheated garage can get below freezing. And I can tell you from experience that an unheated bedroom can, too.
Add an extra layer of pine straw or mulch over perennials and annuals. Tender shrubs can be covered with cardboard boxes or thick blankets. Cover them all the way to the ground and leave the covering open to the ground so the heat radiating from the soil can rise up under the covering.
No plasticDon't cover the plants with plastic. That will encourage moisture lost from the foliage to condense on the leaves and flowers, causing ice crystals that may damage plant parts and cause more damage.
And don't try to spray the plants with water to form a layer of ice on the foliage. You just can't apply the volume of water needed to make this type of freeze protection effective.
Pansies can be frozen solid and still come back.
How can they do that? I called horticulturist Paul Thomas at the university to find out.
"When it gets cold," Paul explained, "most plants die because the ice freezes within the cells and ruptures the cell membranes. This damage either kills the plant outright or allows in disease that quickly finishes off the plant."
Making antifreezePansies and many other perennials, he said, can sense the cold and move water from the cells into the between-cell spaces. They relocate water into the roots, too, where it is less likely to freeze underground.
"When the water is removed, the cell contents inside are concentrated," he said, "and all the sugars from photosynthesis form a simple antifreeze. The pansy may turn a dull, gray green, but it's perfectly happy."
When things warm up, he said, the plants move water back into the cells and come back strong.
I don't know if "sooner" dogs can be frozen solid, but they always come back.