It can get cold in metro Atlanta, but luckily that doesn’t happen very often. Overall, freezing temperatures happen during 36 nights a year on average, from November to March. What can you do to help protect your outside plants when the thermometer plummets?
Q: What’s a “hard freeze”?
A: The term is used to imply temperatures that are sufficiently cold, for a long enough period, to seriously damage or kill seasonal vegetation. In our area, this usually means temperatures at or below 28 degrees F.
Q: What protective steps can you take?
A: When single and lower double digit temperatures are expected, it’s a good idea to completely cover your tender plants — those with a high water concentration — with a cloth. You can use a lot of different things, but a sheet usually works best to help trap ground heat beneath it.
Tender plants commonly found in the Atlanta landscape include Holly ferns, fatsia, indica azaleas, gardenias and elephant ears.
Leave the plants covered until you know that temperatures have been out of the freezing range for at least a 24-hour period or so. That allows them time to warm up. Since leaves get brittle when they’re cold, pulling the cover on and off might damage them.
After the freeze, look at the tips of the plants. If the tips of the leaves look burned, they will turn brown from being burned from the cold.
Then you need to prune off the freeze or frost damage. Don’t make heavy or deep wood cuts. Just prune off the brown part that you know got damaged.
As you start coming into the spring months, you’ll see the full extent of the damage. Take a fingernail and scratch the first layer of bark on a branch or twig. If what’s underneath is green, then the plant is alive. If it’s brown underneath, there’s a greater likelihood that the branch died and needs to be pruned off. Look for other types of spring activity like leaf buds coming out, flower buds, etc.
Q: Are some plants more prone to freezing than others?
A: Since the zone in Atlanta has changed several times over the last century, people are confused about what they can and cannot plant.
The U.S. Department of Agriculture Plant Hardiness Zone Map (planthardiness.ars.usda.gov/PHZMWeb/) is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. Atlanta is in Zone 8.
Tropical plants and those not normally found in our zone are the ones that are going to be damaged by the cold weather.
Q: Any other advice?
A: Water your plants deeply after a hard freeze because both the leaves and the roots have been harmed during the freezing process. So a good, long, heavy watering is necessary for all your plant material.
Another way to help your plants through the winter is by applying a heavy mulch. The more water that is in the leaf of a plant, the more supple the leaf will be and the harder it will freeze, resulting in greater damage.
Things like elephant ears need to be cut back and heavily mulched over the bulb to keep the frost from actually setting on the plant. Much of the damage caused by freezing is the actual frost touching and freezing on the tissue. Although removing the damaged tissue is a good idea, be careful to not go too deeply into healthy stems.
Q: Is constant cold or flip-flopping temperatures worse for plants?
A: The yo-yo effect is more damaging. Plants get a conflicting message, so some of them start pushing out the more tender parts of their leaf tips. That’s where the real deep damage can occur.
Q: What happens if it snows?
A: Actually snow is an insulator. If we get a snow and then longer colder temperatures, the plants would all be protected by the snow.
You might shake the snow off evergreens to keep them from getting pulled out of shape.
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