Wilson Bros Gardens LLC

Where I live and garden in central Georgia there's an old saying that says: "If you don't like the weather one day in Georgia just wait until the next!" This saying probably works for many other states in the US as well, where weather conditions and temperatures can vary daily from one extreme to the other. 

Wild temperature fluctuations can wreak havoc on certain plants; especially when it goes from warm to really cold. 

Damage to plants due to temperature can occur when there's a severe cold front that moves through on the heels of a warm period. This often happens during early to late winter, when an early warm-up can get the juices flowing on some types of plants, causing them to produce tender new growth to early. It's this new growth that can be damaged from freezing temperatures.

If a considerable amount of new growth has been produced during a warm period, the cold can work it's way through the soft, tender leaves into the branches and stems of the plant, which can cause the plant to go into shock, sometimes causing death of part or all of the plant.

Of course, tropical plants, citrus and houseplants are exceptionally vulnerable in regions that experience freezing temperatures. These tender plants should be brought indoors sometime during the fall before night time temperatures fall below 50 degrees F. Native and other hardy ornamental shrubs and trees listed as hardy in your USDA Plant Hardiness Zone usually handle temperature extremes well. That said, many established landscape ornamental plants can suffer cold damage due to drastic fluctuations in outside temperature. 

In the event weather forecasters are calling for freezing temperatures, and your plants have a lot of fresh, tender new growth on them, here are some tips you can follow to protect your plants...

Ceasing pruning of any outdoor plants 45 to 60 days or so before the average first-frost date in your area. Late season pruning can stimulate new growth that can be damaged by an early frost. Essentially, you want to allow your plants to go into dormancy before cold weather arrives. 

Healthy plants that have had proper nutrition will be more tolerant of cold temperatures and recover from injury more rapidly. That said, as with late pruning, late fall-feeding feeding can stimulate new growth that can be damaged by an early frost. Therefore, cease fertilization of outdoor plants two months prior to the first average frost date in your area.

We put heavier coats on when the weather is freezing and many plants will appreciate a coat as well...of mulch that is. Mulch helps the soil retain moisture and protects roots against the cold. It also serves as a blanket of insulation that can keep the soil from freezing during periods of extended cold temperatures. Pine straw or shredded wood are perfect mulches to provide some winter protection to the root systems of plants. These and other mulches are readily available at most nursery and garden centers. A 3- to 4-inch layer of pine straw or a 2-inch layer of shredded wood mulch is advised. Mulch should be added around the base of plants. However, to avoid rot damage, be careful not to put the mulch right up against the trunk of the plant or tree.

The best way to protect the new tender leaves from frost damage is to simply wrap the shrub or plant with a sheet, blanket and/or plastic film. This acts like insulation, keeping the frost off the leaves and warm air from the ground around the plant. That said, it's not a good idea to cover a plant with only plastic as the leaves can be damaged. Only use plastic sheeting on top of cloth sheeting for extra-added insulation.

To secure the covering drape it over the plant so that it is hanging to the ground. Then tie a string around the covering towards the base of the plant as shown in the photo below.

 

Frost usually forms when the dew on leaves freezes in the early morning hours. Therefore, once the sun is up in the morning the cover can be removed. That said, if temperatures remain below freezing you can wait until later in the morning to remove the cover until temperatures rise above freezing.

Remember that the roots of any plant growing outdoors in a container will be exposed to the colder air temperatures. So, in the event that temperatures are to drop below 55 degrees move any tropical plants growing in containers to a warm interior space. Also consider moving even your semi-hardy or tender ornamental plants growing in containers to a protective space, such as a garage or shed or garage. Containers that must be left outdoors should be protected by mulch and pushed together before a freeze to reduce heat loss from the sides of the container. You can also wrap containers with blankets or plastic bubble wrap material. Placing containers against the exterior walls of your home can provide protective radiant heat to plants as well.

Plant coverings, such as a sheet or blanket, can also be helpful, but more for protection from a frost than from extreme cold temperatures. We often do this at our nursery in late winter or early spring when fresh new growth has emerged and there comes a late frost. 

Dry roots are more likely to suffer from cold damage. Well-watered soil is capable of absorbing more solar radiation than dry soil, and will re-radiate heat at night. When freezing temperatures arrive, moisture in the soil will also form an insulating sheath of ice around plant roots protecting them at 32 degrees F. So, anytime freezing temperatures are forecast, especially a deep freeze, it's a good idea to check soil moisture and deep soak the soil if it's dry.

Plants known to be tender, such as some varieties of gardenia, palms, fig trees, and elephant ears, should be planted in a site that is protected from northern and western winds in frost-prone areas. This means you'll want to plant them on the south or east side of the home or other structures, or in a protected location such as a courtyard where they'll be sheltered from the wind by walls. You can also provide barriers to protect tender plants from cold winds by shielding them with adjacent plantings, fences or buildings.

In the event there is heavy snow use a broom to brush snow off plants that are susceptible to damage. That said, if snow or ice is light and not posing any problems, and temperatures are forecast to drop much lower after the snow, leave snow on plants to serve as protective insulation from the colder air temperatures.