Frost & Freeze Protection

Some patchy frost is possible early Saturday morning though some light winds and marginal temperatures make the chance low around Charlotte but higher for the foothills and northwest piedmont. Remember frost can form even with air temperatures of 33-38 degrees. The temperature near the ground due to radiational cooling can be much lower. I think 36-38 is possible Saturday morning in Sheltered locations.

1. If you can bring them inside the garage or house or even onto the porch. Anything closer to the house will help. All objects reflect or emit longwave radiation which can keep plant warmer. Beds and gardens farther from the house and trees will get the coldest. An open sky is bad this allows from the maximum radiational cooling so protect those plants first. Basically, the more sky that plant can see the colder it will get at night.
2. Today when the sun is high in the sky water your plants heavily. This water will help absorb heat today and trap it in the soil and plant. This will work much better than you think. Not only will the ground absorb heat the plants will as they suck up the water. Then at night the plants and soil that have more moisture cool much slower than dry soil and plants. This worst great for frost or light freeze set-ups.
3. You can heavily mulch your beds with leaves, straw or mulch to help protect the plant. The key here is to do this during the heating of the day you want to trap as much heat from the sun in the ground, mulch, and plant during the day, so that has it for tonight.
4. Then of course, once the sun goes down cover your plants. The best materials are fabrics and not plastics. If you cover them soon after sunset, you will trap the maximum amount of heat for tonight. Be sure though to uncover them as soon as the temperature warms in the morning or the sun gets higher in the sky. Leaving them covered with the sun up can cause damage as well. Never use plastic if at all possible this will cause damage.

When all else fails…WATER!

Last-ditch efforts are turning the sprinklers on. It sounds weird, but watering during a freeze will work for short periods of time and down to only certain temperatures but it works. It has nothing to do with a layer of ice insulating the plant. Water contains heat which when removed by the air causes it to freeze into ice. That heat removed has to go somewhere, and this “latent heat” release will go into your plants and the surrounding air saving them from freeze damage. This tiny bit of latent heat will work down to temperatures around 27°-28° but only for a few hours. Those long hard freezes might be a lost cause. This is a last-ditch effort and works for a freeze.