By: Robyn Stewart
Did you know that cold damage to ornamental plants can be a significant issue in Georgia? Now that temperatures are starting to drop just in time for Christmas, there are a few practices you can follow to help protect your plants this winter.
Most ornamental plants actively grow and reproduce during the warm, long days of the summer, and during this time any frost or cold weather can cause significant damage. Come late summer and early fall, the plants undergo a process called cold acclimation, which is triggered by cooler temperatures and shorter day lengths. If the plants undergo cold acclimation too early, they have a shortened growing season. Too late, however, and they may be injured at an unexpected early frost. While we unfortunately cannot control the weather, practices like plant selection and maintenance can affect how plants acclimate for winter.
There are several types of damage you might see on an ornamental plant that are due to cold weather. The most common damage is characterized by brownish-black, mushy, dead leaves and stems on the plant. This occurs when the water in the plant cells freezes into ice, killing the tissue. Plants that are acclimated to the cold will usually survive this type of injury, but plants who are not acclimated may have extensive injury to their root system, resulting in extensive damage or death. Typically, you will not notice this damage until the next spring when the plant won’t leaf out. Another type of damage is desiccation, or the drying out of the plant due to windy, cold weather. The leaves may be partially or completely brown and defoliate from the plant. In fluctuating temperatures, flower and leaf buds can be damaged, which can reduce or eliminate blooms and foliage the following spring. A final injury you may see is bark splitting, which appears as loose bark in various areas on a tree’s trunk. The split can expand into a frost canker, which can cause structural damage to the plant and result in death.
There are a variety of different cold-related injuries a plant can experience, but there are also a variety of things you can do to prevent them. The best, most effective way to prevent cold damage is to select plants that can tolerate the environment in your area. We are in plant hardiness zone 7B in Lincoln County, so selecting plants that are graded for our area will help them survive both our winter and summer climates. Furthermore, placing plants in the most appropriate spaces on your property is important too. The coldest spots on a property are often on the north and northwest areas of the property or in low spots, while the warmest areas are usually on the southern end of the property. Windbreaks and canopy plants like trees can help protect plants from cold injury as well. Other things to consider are elevation, soil property, and proximity to structures and other plants—all of which can affect the temperature and microclimate of the area. Maintaining proper soil nutrition can help a plant stay healthy throughout the winter, and this includes timing your fertilization and pruning properly. Do not fertilize or prune plants in the fall as these practices can cause a flush of new growth that can be damaged when temperatures drop. A final way to protect your plants is to consider covering or heating them. This might be bringing them in a house, shed, or greenhouse, or by placing a protective cover such as a sheet or cardboard box on them. Generally, container plants are more susceptible to cold weather than ground-planted plants, so consider wrapping their containers, covering them, or relocating them. The use of mulch can also help protect root systems and reduce soil heat loss.
If you have questions on how to protect your valuable ornamental plants this winter, let us know at uge3181@uga.edu or 706-359-3233.
