Did you know the first recorded incidence of snowfall in Augusta was in 1968, the greatest one-day snowfall was 8 inches in 2010, and our largest season of snowfall totaled 14.4 inches in 1973? While I’ve lived all over the east coast, including snowy New York, it is always an exciting anomaly when we get snow here in Georgia. With that said, there are a few things the ag agent in me starts to think about during these periods of prolonged cold weather.
Cold damage or injury can occur on all parts of a plant, including the fruit, stems, leaves, trunk, and roots. During cold weather, the water within the plant’s cells freezes to ice, causing the plant tissue to die. This causes mushy, brown-black tissue on the leaves and stems. Cold injury is prevented naturally by a process called cold acclimation, that occurs as a response to cooler fall temperatures and short days. During this time, there are changes to the plant structure (cell wall) and metabolism (energy production) that allow the plant to withstand cold injury. Plants that are not acclimated often sustain severe injury to the root system and will be damaged or killed.
Another type of injury we might see due to cold, windy conditions is desiccation. Desiccation is the drying-out of the plant, and results in leaf scorching or burns on the tips of leaves, often causing them to turn brown and fall off the plant. The use of a windbreak such as a fence, building, or other plants can help protect from this type of damage. Bark splitting can also happen in woody plants during cold weather. A frost canker can form, appearing as a dark, moist area, and resulting in loose bark around the trunk. Bark splitting can cause structural damage, reduce the ability for the plant to transport nutrients and water, allow secondary issues like insect infestation, and result in the death of the plant.
Early in the spring, we may see damage to leaf and flower buds as a result of cold snaps or late frosts. This damage can cause a reduction or total loss of blooms and damage of foliage. An easy example we’ve dealt with in the past few years is loss of blueberries in the early spring. Damage of buds can be evaluated by cutting them open – if they are green throughout, they’re healthy; if they’re brown or dark, they’ve been injured.
There are a few things that can be done preventatively during periods of cold. First off, be sure to select plants that are adapted to our hardiness zone (8b), which means they can tolerate our low temperatures (15-20 degrees, on average). Place cold-sensitive plants in warm, sunny parts of your property, near larger plants, or near structures to help them stay warmer. Maintain plant health through practices such as fertilization, pruning, and transplanting – but be sure to time these actions properly. Many of our management actions can cause a flush of new growth, which is undesirable in the late fall as we head into winter, since new growth is more likely to be damaged by the cold.
A few actions can be taken to reduce the impact of cold snaps on plants. First, canopies (such as a protective structure, shed, overhang) and coverings (burlap, sheets) can help reduce heat loss from the soil and plants, keeping them warmer than the ambient temperature. Container plants, in particular, can be susceptible to cold temperatures, since their roots are not insulated by the soil. Plants should always be uncovered during the day, as solar heat can be trapped and have other consequences than the cold. Finally, be sure to provide adequate water, even in winter. Moist soil absorbs more heat and maintains elevated temperatures around plants, and mulching the base of plants can help retain that moisture.
Cold damage may not be evident for days or weeks after the cold event. To determine if plants have damage remove several buds, stems and leaves (if present) from the plant. For buds, use a knife to cut a cross section of it’s top. If there is any discoloration, it has been damaged. For stems, 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. For leaves, damage may appear as obvious black or burnt foliage, usually occurring at the tip of the branches. If one area of the plant is affected, the whole plant may still survive. Wait until freezing weather has passed in the spring to prune back cold-damaged areas on limbs several inches below the injured tissue. No pruning is necessary for injured buds.
