Regional Gardening Reports :: National Gardening Association

In the Garden:
Lower South
December, 2005
Regional Report

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

Tis the Season to be Freezin'

Winter in our region 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.

In order for our plants to develop maximum hardiness, they need the weather to become progressively colder over time. Warm days followed by a really cold snap are a recipe for serious plant injury.

Each year, as cold weather threatens, we go to great (and often strange) lengths to safeguard our plants from cold damage. Some techniques work well, others don't. 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 home.

Giving Plants a Fighting Chance
On a very cold night, I'll cover marginally hardy container and in-ground plants with some old blankets or a section 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 freeze them.

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.

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 to the ground, rather than wrapped around the plant and tied around the trunk. Those "landscape lollipops" don't get much, if any, protection.

When our soil gets on the dry side, I'll 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 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.

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, contrary to some opinions. 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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