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DALY: Protecting landscape plants from the unseasonably cold weather

Timothy Daly

Timothy Daly

Area homeowners are concerned about the effect of the recent hard freeze will have on their garden plants. The chances of cold weather having a detrimental effect on plants can be reduced by taking measures to ensure landscape plants can tolerate and survive hard freezes.

Gwinnett County is located in USDA hardiness zone 7b. This means that our winter temperatures have the potential to drop to as low as 5 degrees as it has in the past week. Are the trees, shrubs and other plants in your landscape adapted to this zone? Most outdoor plants sold at local garden centers and nurseries should be hardy here. On the other hand, purchasing and installing plant material that is better adapted to warmer climates, such as oleanders, Japanese pittosporums and most palms, places these plants at a greater risk of suffering from hard freezes.

Have your plants been properly located and planted in the yard? Some shrubs such as azaleas and camellias can suffer from cold injury when planted in sites with open exposures to wind and full sun. Always plant them in locations where they will receive adequate protection against these elements.

Throughout the growing season, make sure your landscape plants receive the appropriate care, such as proper watering, fertilization, pruning and pest control to maintain optimum vigor and growth. Plants that are weak, unhealthy and poorly maintained are more vulnerable to cold weather.

You can take several steps to reduce the likelihood of cold damage. Always maintain a two to three inch layer of mulch around plants at all times because it insulates the roots and protects the soil from rapid temperature fluctuations. Provide adequate water to newly planted shrubs and trees to keep them hydrated and prevent the plants from drying due to cold air and frozen soil.

A bronze coloration of the foliage, particularly on certain azaleas and boxwoods, may be observed just a few days after a hard freeze. On privet, ligustrums and camellia the foliage often turns purple. The discoloration is simply the plant’s response to a sudden chill and is perfectly normal.

After a hard freeze, examine the plant material for damage; however, it is sometimes difficult to ascertain cold damage a day or even a week after a severe freeze. Cold damage may go unnoticed until the plant fails to come out of dormancy in the spring. A simple way to determine if the plant material is actually dead or alive is to scratch the bark with your fingernail. If the stem tissue is green or white where you scratch, that wood is still alive. It should put out new growth in the spring. If, however, the stem tissue is brown or brittle, then that branch is dead. The deadwood should be removed in the early spring after freezing weather has passed.

Although we have no control over the weather, you can improve the chances of your landscape plants surviving these temperatures with the proper selection of plant material along with appropriate care and maintenance. If your landscape plants are in good health, properly maintained and are adapted to the cold temperatures in our area, they will have an increased probability of surviving the occasional hard freezes.

Winter is also a good time to decide on what to plant in your yard. The Gwinnett County Extension Plant Sale has some excellent plants, including several fruit trees, available for sale this winter. Go to the extension website at www.gwinnettextension.com to download the order form or call the Gwinnett County Extension office for a form to be mailed to you.

Timothy Daly is an Agricultural and Natural Resource Extension Agent with Gwinnett County. He can be reached at 678-377-4010 or tdaly@uga.edu.