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Freezing Weather—How Bad on Plants?

 

By Marc Teffeau, Cherokee County Master Gardener

 

A question that I am sure is on many Cherokee County gardeners’ minds is how much damage my plants received from the record-breaking low temperatures we experienced in late December of 2022. So, did those temperatures kill the plants or just set them back? The answer is “it depends.”

According to the Georgia Master Gardening Handbook, “freezing injury is a complex phenomenon governed by a number of factors, including genetics, the minimum temperature level, the speed at which the temperature dropped, the duration of the below-freezing temperatures, the degree of the hardiness of the plant at the time of the freeze, and the nature of the frees (i.e., whether the freeze is accompanied by wind or occurs suddenly following several days or weeks of warm weather.)”

Another factor that impacts freezing damage is the plant’s location in the landscape or its “microclimate.” For example, plants on the north and northeast sides of a house may suffer more damage than those on the south and west side. Conversely, plants protected from wind exposure by walls or fences will be less likely to have damage.

UGA Extension Publication Circular 872 “Winter Protection of Ornamental Plants” indicates that “cold injury can occur on all parts of the plant including fruit, stems, leaves, trunk and roots. Typically, homeowners notice the cold damage first on the leaves and stems. Ice forms within the plant’s cells, the plant tissue dies, and leaves or stems become brownish-black and mushy. Cold acclimated plants can often withstand this type of ice formation. Plants that are not acclimated may sustain injury to the root system and may be severely damaged or killed. Sometimes this is not noticed until the plant fails to leaf out the following spring.

“Windy conditions and accompanying cold also may cause plant damage through desiccation (evaporative water loss exceeds water absorption). This is the drying out of the plant. Marginal leaf scorching or leaf-tip burn is characteristic of this problem. Leaves may eventually turn completely brown and defoliate.

 “Damage to flower and leaf buds can occur during periods of low or fluctuating temperatures. This can lead to a reduction or total loss of blooms and damage of the foliage the following spring. Damage can be appraised by removing several buds and cutting them open to reveal their condition. If they appear green throughout, they are healthy; if they are partially brown or darkened, they have been injured.

“Cold damage may not be apparent in the plant for several days or weeks. To determine if your plants have been damaged by the cold, wait several days after a freeze and remove several buds, stems and leaves (if present) from the plant. Use a sharp knife or razor blade to cut a cross section of the bud’s top. If there is any discoloration in the bud, they have been damaged.

“To determine if stems have been injured by the cold, peel the bark back to reveal the cambium layer (layer directly under the bark). If there is any black or brown discoloration, damage has occurred. Leaf damage may appear as obvious black or burnt foliage, usually occurring at the tip of the branches. Damage on buds, stems and leaves may be localized and the entire plant may not be affected.

“Waiting to prune after freezes have passed will guard against removing living wood. If localized damage has occurred to the foliage or stems, prune several inches below the injured tissue. Although injured buds may reduce or eliminate flowering or leaf emergence in the spring, no pruning is necessary.”

Fortunately, ornamental trees and shrubs can leaf out again if the initial growth is damaged or destroyed. Damaged trees and shrubs have only suffered a temporary setback. If your shrubs and trees are healthy and well-established in the landscape, they will produce additional growth to replace the damaged foliage within a few weeks. However, this “re-flushing” will put some stress on the plant’s reserves. As a result, it is important to give the freeze-damaged woody ornamentals some extra attention during the growing season. This attention includes watering during dry periods and perhaps some additional fertilization to aid in the plant’s recovery.

Georgia can experience freeze damage both in winter and in spring, after new foliage has begun to emerge. This tender foliage may be subject to freezing damage for perennials in the landscape. The foliage may turn brown or be twisted in shape and off-color. If the freeze is short in duration, the roots and crowns of the perennial plants, especially mulched plants, should not suffer any damage. Perennial plants will respond to the freezing damage by sending out new foliage to replace the damaged leaves. However, on fruit crops, depending upon the cultivar and how far the fruit blossoms may have opened, we may see reduced blueberry and fruit tree crops, especially on early flowering cultivars.

For more information, see the UGA Extension Publication Circular 872. It can be found in the “Publications” tab on the UGA Extension website: https://extension.uga.edu/

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