The lowest temperatures in years have descended upon Henry County recently, making life miserable for people and plants. And now area gardeners are asking how extensively has the cold harmed their landscape plants. The answer to this question depends mainly upon your response to the following questions.

First, are the trees, shrubs, and perennial plants in your landscape cold hardy? Are these plants suited to our local weather conditions and our climate zone? Henry County is in USDA hardiness zone 7B, which means that our winter temperatures have the potential to reach lows of 5 degrees to 15 degrees. Plants purchased locally from reputable garden centers and nurseries should be hardy here. On the other hand, plants adapted to warmer climates may be tender here and, therefore, are less able to survive our colder winters. Examples include all citrus plants, oleanders, Japanese pittosporums, and cycads.

Second, have your plants been appropriately located and planted in the yard? For example, some shrubs like azaleas and camellias suffer from cold injury when placed in sunny, open exposures. Always place these plants where they will receive adequate protection from too much winter sun and wind. All plants have specific environmental requirements, so keep these in mind when planting.

And the third question is, have I provided the proper care for my landscape plants throughout the growing season? Have they been watered, mulched, fertilized, pruned, and sprayed when needed to maintain optimum vigor and growth? Weak, unhealthy, or poorly maintained plants are usually the first to suffer during periods of frigid weather.

Ascertaining cold damage, a day or even a week after a severe freeze can be difficult. Often, you will only know the extent of it come spring, and you can better evaluate how much damage has occurred. The winter injury will become apparent when plants fail to leaf out in the spring or flower later. After a few weeks of extremely cold weather, you may observe a bronzing of the foliage, particularly on azaleas and boxwoods. The privet, ligustrum, and camellia foliage often turn purple after freezing weather. This discoloration is the plant’s response to a sudden chill and is perfectly normal. The foliage is alive, and the change in coloration is its response to the cold.

On the other hand, frozen or dead foliage almost always turns brown. In many cases, leaves curl, roll up or drop from the stems. Using your fingernail to scratch the bark, you can determine if a branch is dead or alive. If the stem tissue is green or white where you scratch, that wood is still alive. This wood should put out new growth in the spring. If the stem tissue is brown or brittle where you have scratched, then that branch is dead. This wood should be removed in early spring after freezing weather has passed.

Azaleas, camellias, gardenias and hydrangeas, and other plants often experience some bark splitting because of extremely cold weather. You can see this damage on lower stems and branches near the soil surface. Injury from split bark appears as dead twigs and branches later in the year.

You can take several steps to reduce the damage to the plants in hard freezes:

Maintain a two-to-four-inch layer of mulch around plants; if the level falls below, add more. It helps to insulate root systems much like fiberglass helps to insulate your home from cold weather. Mulch also helps to protect the soil from rapid temperature fluctuations, which are a primary cause of cold damage.

Avoid pruning until late February or March to shape most evergreens and summer-blooming plants. Extensive corrective pruning, where several feet of the plant is cut back, on plants such as hollies can be done during the early spring. Remember to prune spring-blooming plants, such as azaleas, forsythia, and spirea, after flowering.

Avoid fertilizer applications during winter, which, like pruning, may stimulate growth that future freeze conditions would likely injure or kill. Delay until late March or April when all the new growth is appearing.

Cover tender plants with old quilts, blankets, or sheets to help reduce frost and cold damage. This technique may only be practical for some plants but is helpful to protect special shrubs, small fruit trees, semi-hardy plants, etc. Placing sticks or poles to prop up blankets, quilts, or other heavy covering may be necessary to prevent branches or limbs from breaking. Plastic can also be used as a nighttime cover but be sure to take it off on sunny or warm days to prevent heat damage to your plants.

Though we occasionally experience bitterly cold temperatures, our landscape plants should suffer minimal damage if they receive the proper care and protection.

Timothy Daly is an Agricultural and Natural Resource agent with UGA Extension Henry County. He can be contacted at 770-288-8421 or tdaly@uga.edu.