Regional Gardening Reports :: National Gardening Association

In the Garden:
Lower South
December, 2013
Regional Report

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You can extend the season on a row of vegetables with a PVC tunnel covered with clear plastic.

Helping Plants Survive a Cold Snap

Winter in the Lower South is a series of brief and erratic breaks in an otherwise long growing season stretching from fall to spring. We live between the northern zones, where there is a REAL winter season each year, and the subtropics, where freezing weather rarely, if ever, arrives. As a result, our landscapes include many plants that are marginally hardy and need some help to make it through an unusually cold winter. Here are some suggestions for strategies you can use to help your plants weather a cold snap in good condition.

  • On a very cold night, cover marginally hardy container and in-ground plants with some old blankets or a section of the spunbonded polyester frost cover fabric. For extra protection you can place a sheet of plastic over a blanket to help hold the warm air underneath, but don't allow the plastic to contact the plant's leaves or it can freeze them.

    Blankets keep us warm because they help contain 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 extend down to the ground.

  • In vegetable gardens, a row of PVC hoops pushed into the soil along a row of plants and covered with clear plastic makes a great mini greenhouse. Open the ends on sunny days to prevent overheating and then close them before a cold night is expected.

  • If the weather has been dry, give plants a good watering a day or so in advance of a predicted freeze. Drought-stressed plants are more susceptible to cold injury. Moist soil is also 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.

  • Take care not to overwater, however. Soil dries out much more slowly in winter. Soggy, waterlogged soil excludes oxygen from plant 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, contrary to some opinions. In fact it can do more harm than good.

  • Pile leaves around perennial plants. A thick blanket of leaves can help protect marginally hardy 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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