In the Garden:
Lower South
November, 2001
Regional Report

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Tender perennials like these pentas need protection from frosts that can kill the tops, and hard freezes that can kill the entire plants.

'Tis the Season to be Freezin'

Our first hard frosts and freezes are just around the corner. When cold weather threatens, we gardeners go to great (and often strange) lengths to safeguard their plants from cold damage.

We live between the northern zones where there's a REAL winter season each year and the sub tropics where freezing weather rarely if ever arrives. Our landscapes thus include many plants that are marginally hardy and need some help to make it through an unusually cold winter.

In order for 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.

Container Plants

Plants in containers are especially susceptible. Roots may be injured even when the above ground parts survive a cold snap. Such injury is often not evident until months later when warmer temperatures begin to place increased demands on the plant.

To protect container plants, group them closely together in a protected location up against the house. If very cold temperatures are forecast, cover them with a blanket for the night.

Bring Out The Blankets

The best way to protect in-ground plants from the cold is to cover them with a thick plant cover fabric or blanket. If more than one night of protection is needed, remove the covers during the day to allow the sun to warm the soil and then cover them again late in the day.

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 be wrapped around the plant and tied around the trunk. Those "landscape lollipops" don't provide much, if any, protection.

Providing Supplemental Heat

Two other handy items are a mechanic's light or string of outdoor Christmas lights. These can be placed under the covers to give added heat. Just take the obvious precautions to avoid fire hazards and electrical shorts. Also take care not to allow a hot light bulb to contact and damage plant tissues such as the trunk or branches. Use lights beneath a cover to protect valuable but marginally hardy plants like a Satsuma orange tree or a kumquat bush. The heat from lights can also make the difference for an in-ground bougainvillea on a really cold night.

When a freeze is forecast, give plants a good watering a day or so in advance. 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. Just don't overdo it as soggy soil for extended periods of time can kill roots.

Finally, use leaves to mulch perennial plants. A thick blanket of leaves can help protect marginal perennials. That first hard freeze will surely arrive in the near future. I just hope all this balmy weather isn't fooling the plants into not preparing for what is certainly just around the corner!


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