By Mike Isbell
University of Georgia
Wow. It’s been really cold this winter.
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 worry
Back 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 plastic
Don’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 antifreeze
Pansies 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.
