Near-freezing temperatures on Sunday gave way to crisp mornings and spring-like afternoons. Forecasts for the upcoming weekend remind us that summer is now only a memory and frost and freezing conditions should be anticipated in the very near future. Temperatures below 32 degrees are unusual in Dalton on Oct. 15. The probability of a first freeze by Nov. 15 is 80%.

Both garden and landscape plants are vulnerable to damage from freezing temperatures. Perennial landscape plants are conditioned to survive cold by acclimation. As days shorten and temperatures decrease, plant metabolism changes to divert nutrients away from new growth and instead increases the concentration of soluble compounds in plant sap. This protects plant tissues by lowering temperatures at which ice crystals form, similar to the nature of antifreeze in a car radiator.

A plant’s response to cues of temperature and day-length are modified by regional adaptation. A plant adapted to colder temperatures may begin cold acclimation earlier.

Limiting cold damage to perennial plants begins by selecting plants that are appropriately adapted. Whitfield County lies within the U.S. Department of Agriculture's Plant Hardiness Zone 7a. Selecting plants adapted to climatic conditions typical for that zone provides likelihood of plant survival, both to cold as well as hot temperatures.

Properly locating plants when they are installed can also contribute to protection from cold injury. During winter, the coldest spots are often found on the north and northwest part of the property and in low areas where cold air settles. The warmest spots are usually on the southern part of the property.

Elevation, land form, soil properties, canopy cover and proximity of structures or other plants determine a microclimate. Microclimates can be used to help protect plants by placing cold-sensitive plants near the part of the house that receives southern exposure or near larger plants or other structures.

Maintaining proper plant nutrition increases a plant’s tolerance to cold injury. A plant that has been given the appropriate nutrition is healthier and more capable of acclimating to cold temperatures.

Adequate potassium status is often associated with persistence through the winter. On the other hand, timing of nitrogen applications must be considered. Fertilizing with nitrogen in the fall, after September, may cause a flush of new growth that is more susceptible to cold temperatures. Soil sampling is the best method to determine your plants’ nutritional needs.

Pruning in late summer or early fall may also stimulate new growth that is more susceptible to cold injury. Most plants should be pruned just prior to the appearance of new growth in late winter or early spring. Plants transplanted in late fall or early winter are also more susceptible to cold injury. These plants may not acclimate properly when exposed to low temperatures.

Plants continue to have water requirements during the winter months. Adequate watering is essential for a healthy and cold hardy plant. Check the water needs of plants prior to a predicted cold snap and water if necessary. Moist soil absorbs and radiates more heat, helping to maintain an elevated temperature around the plants. Mulching the base of plants helps to retain moisture.

When forecasts warn of freezing temperatures, sensitive plants may be protected either by placing them inside a protective structure (house, garage, greenhouse or shed) or by placing a protective covering over them.

Container plants are especially susceptible to cold temperatures; their roots are more exposed because they are above ground. Plants with roots that are damaged by cold temperatures may not show immediate signs of damage; these plants will show signs of stress when temperatures rise and the demand for water from the roots is greater. Push together container plants that are left outside and mulch or cover them to decrease heat loss from the sides of the containers. Wrap the bases of the containers in plastic, burlap or blankets to reduce heat loss.

Covering plants with sheets, blankets or cardboard boxes helps protect them from low temperature injury. Plastic sheeting is not recommended; the plant can heat up rapidly as temperatures rise and be damaged. Remove the cover and provide ventilation during the day to allow the release of the heat that is trapped by solar radiation. You can build a frame from PVC or similar material to keep the cover from coming in contact with the plant and possibly breaking leaves and stems.

University of Georgia Extension Circular 872, “Winter Protection of Ornamental Plants,” provides detailed information about limiting winter damage to the landscape.

Roger Gates is the agricultural and natural resources agent for University of Georgia Extension, Whitfield County. Contact him at roger.gates@uga.edu.

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