Regional Gardening Reports :: National Gardening Association

In the Garden:
Lower South
December, 2003
Regional Report

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A cover supported by PVC hoops can help protect plants during sporadic hard freezes and keep the garden going all winter long.

Protecting Semi-Hardy Southern Plants

Here in the south our typical winters are fairly mild with some erratic but brief periods of cold weather. We do not experience the severe cold weather of our northern neighbors, but we have too much cold to grow the plants common in the warmer parts of the Gulf Coast. As a result, our landscapes include many plants that are marginally hardy and need some help to make it through an unusually cold winter.

Each year as cold weather threatens, we go to great lengths to safeguard these plants from cold damage. Some techniques work well, and others don't. Most of the time our freezes are fairly brief in duration. This makes protection easier since simply covering plants and slowing the temperature drop will often get them through.

Preparing for Cold
Container plants are especially susceptible to a bitter cold snap. To protect my container plants, I group them closely together in a protected location up against the house.

On a very cold night, I cover my marginally hardy container and in-ground plants with some old blankets or several layers of the spunbound polyester frost cover fabric. Sometimes I'll also place a sheet of plastic over a blanket to help hold the warm air underneath. Don't allow the plastic to contact the plant's leaves or it can damage them.

Blankets keep us warm because they help hold in the heat that our bodies produce. Plants do not produce heat for the cover to hold in. The heat we are trying to contain is in the soil. Therefore the covers should go over the plants and to the ground, rather than be wrapped around the plant and tied around the trunk. Those "landscape lollipops" don't get much, if any, protection.

Giving Plants an Edge
When our soil gets on the dry side, I give plants a good watering a day or so in advance of a freeze. Drought-stressed plants are more susceptible to cold injury. The moist soil also is a good heat sink, absorbing heat during the day and radiating it out slowly on a cold night. Combined with a cover, it can make a small but important difference.

Of course we must take care not to overwater, creating a waterlogged soil condition. Soil dries out much more slowly in winter. Soggy soil excludes oxygen from the roots, often resulting in root loss and attack by root-rotting fungi. Sprinkling the foliage and branches of plants prior to a freeze does NOT help protect them. In fact, it can do more harm than good.

Finally, I pile leaves around perennial plants. A thick blanket of leaves can help protect marginal perennials, such as butterfly ginger (Hedychium), esperanza (Tecoma stans), and firebush (Hamelia patens). They well are worth the extra effort to help them make it through the winter.

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