Protecting plants from cold temperatures
By Eddie Smith
Although we live in the South, winter sometimes brings cold temperatures that can cause severe damage to many of our landscape plants.
Late frost after temperature rises in March or April could be even worse than the same cold temperature in winter. Thus, it is important to protect plants from these cold temperatures.
Temperature changes can damage plants in several ways.
A plant’s ability to withstand cold temperatures depends on plant species, and how low and how fast temperatures decrease.
When temperatures gradually decrease, a plant can acclimate, or adjust itself, to withstand colder temperatures better.
Sudden decreases in temperature cause more damage in fall or early winter than similar low temperatures well into winter. If temperatures increase during the winter months, some plants may break dormancy, or deacclimate, and begin leafing out or flowering. Plants that break bud dormancy become more susceptible to late frost because of their new, tender growth.
Cold injury can occur to all parts of the plant (flowers, fruits, leaves, stems, trunks, roots, and buds).
Fruits and flowers are the least tolerant of cold injury because they have little ability to adjust or build up tolerance to colder temperatures.
Leaf and stem tissues are injured and damaged when ice forms within the plant’s cells that typically occurs during a rapid freeze. When this happens, the plant’s tissue dies and is often characterized by plant parts turning brown and mushy. When the temperature drops slowly, ice sometimes forms between the walls of the plant’s cells. Hardy or cold acclimated plants can often withstand this type of ice formation.
Windy conditions can also cause plant damage by desiccation, or the drying out of the plant. Marginal, or leaf-tip, burn or totally brown leaves in severe cases characterize desiccation. Desiccation occurs when a plant loses more water than it absorbs, or takes up, by the roots, especially when the ground is frozen.
Homeowners can enjoy a wide variety of plant materials. They can increase their choice of available plants by assessing and maintaining plant needs and by carefully selecting plants and site locations. By planting a combination of tender and hardy plants and by protecting plants susceptible to cold temperatures, homeowners can have landscapes that survive cold temperatures.
Existing plants can be protected by making sure they are well watered right before a freeze.
Young citrus trees should be protected with a blanket or sheet. A covering of plastic is excellent protection.
Build a frame over the plant or plants, cover with plastic, and seal plastic to the ground with soil. Shade plastic to keep temperature from building up inside. This plastic traps moisture and warm air as it radiates from the soil. It also knocks off cold wind. Be certain not to allow plastic to come in contact with plants.
Eddie Smith is the MSU-ES Pearl River County Agriculture Agent/County Coordinator