Cold damage may not show up until spring
SALISBURY — Unexpected temperature extremes are not unusual for Rowan County, but the extreme blast earlier this week caught many by surprise. You might be curious to know if there was any plant damage due to the below-normal dip in temperatures. There is a possibility of damage, but with some crops and plants, there is really no way to know at this moment if cold damage did occur. Even acclimated plants can be hurt by temperature extremes.
Cold damage may occur immediately, but often the damage does not manifest itself until early summer. Windy conditions on cold sunny days can 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. Late fertilization does not allow plants adequate time to harden off or acclimate for the winter. Tender, succulent growth is often damaged by freezing weather, especially following a period of unseasonably warm weather.
Azalea and camellia stems and branches often rupture or crack after a sudden freeze. The 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 vessels are damaged as the bark adsorbs heat during a sunny day and splits and cracks as the temperature plummets in the evening. These trees often bloom normally in the spring and then immediately die.
So, what can we do to protect our landscape plants? With our uncertainty of weather, it’s not unreasonable to expect more like we had earlier this week. Below are a few precautions that will help prevent winter injury.
• Select plants that are hardy to our region. Many of our plants are marginal (some gardenias) and burn easily with temperature extremes. Purchase plant materials that grow in zone 7, which will be on the labels of ornamental trees and shrubs.
• 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 crape 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.
Go to http://www.ces.ncsu.edu/depts/hort/consumer/weather/coldprotect-shrubs.html for more detailed information on how to protect trees and shrubs from cold injury.
Darrell Blackwelder is the county Extension director with horticulture responsibilities with the North Carolina Cooperative Extension Service in Rowan County. Learn more about Cooperative Extension events and activities by calling 704-216-8970 Facebook or online at www.rowanextension.com
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