Cold weather damage may not show up until later

Published 12:00 am Friday, January 16, 2009

If you’ve lived in Rowan County for any length of time, you’re no stranger to our temperature extremes.
It’s winter for sure, and this frigid weather can take its toll on plants, especially newly planted trees and shrubs. Warm weather exactly one week ago only exacerbates the problem. Even acclimated plants may be damaged with this cold weather.
Cold damage may occur immediately or it may not manifest itself until late spring or early summer. Windy conditions on cold, sunny days often burn evergreen trees and shrubs. Leaf margins and tips of camellia, rhododendron and azaleas often are victims of leaf burn or scorch.
New plantings that are not properly acclimated may also have winter damage. Fertilization in late summer does not allow plants adequate time to harden off or acclimate for the winter. Tender, succulent growth is often damaged with freezing weather, especially following a period of unseasonably warm weather.
Azalea and camellia stems often rupture or crack after a sudden freeze. This damage is generally not evident until mid-May when sections of azalea shrubs turn brown and die.Ornamental cherry trees, flowering plum and other ornamentals in the Prunus family have dark, thin bark easily damaged by cold weather. The tree’s cambium, or food-conducting vessel, is damaged as the bark adsorbs heat during a sunny day and splits and cracks as the temperature plummets at night. Generally, the tree blooms as normal in the spring and then dies almost immediately. This phenomenon also happens to other ornamental trees such as Japanese maples.
So, the big question is what can we do to protect our landscape plants?
– Select plants that are hardy to our region. Many of our plants are marginal (some gardenias) and burn easily with temperature extremes.
– Apply at least 6 inches of coarse mulch to insulate and conserve moisture during the winter months.
– Do not fertilize plants in late summer or early autumn with excessive nitrogen. However, plants need to be healthy. Keep the plants well fertilized and free from insects and disease.
– Avoid pruning in fall and early winter. Pruning stimulates growth which is often killed with late frosts and freezes. Many crepe myrtles have been killed outright by excessive fall pruning.
– Keep plants irrigated during late summer and the fall to prevent drought stress. Drought-like conditions predispose plants to winter injury and cankers.
– Pack potted plants close together and mulch or mound soil around pots and balled and burlapped plants to insulate the roots.
Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County; call 704-216-8970 or see http://www.