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Spring is right around the corner, but winter weather still poses a threat to trees and ornamental plants in the mid-south landscape. Extreme cold, drying winds, bright sunlight, and large temperature swings are common causes of winter injury. Actions can be taken to reduce the chance of winter injury and to help trees and ornamental plants recover from damage.
This time of year, with bright sunlight during the day and low overnight temperatures, winter sunscald is a problem for young trees. Trees with thin bark such as young maple, magnolia, cherry, and crabapple may be damaged in winter when their bark surface is warmed by a bright winter sun and then rapidly chilled as temperatures drop overnight. The bark tissue and cambium are killed by the rapid temperature change. Damage is not visible immediately, but in the spring, dead bark falls away resulting in an elongated wound. This type of injury characteristically occurs on the south and west portion of the trunk where warm afternoon sunlight is most direct.
Winter sunscald can be prevented by wrapping the trunk of recently planted trees with burlap, sissalkraft, paper, or other tree wrapping products. The wrap should be kept on tree trunks from November through April (when overnight lows can be below 32F) and taken off during the warmer months to allow the trunk to harden to the elements. Trunk wrapping should continue for the first three years, on susceptible plants, after planting until the tree trunk has thickened and is strong enough to protect the inner cambium layer from injury.
Low temperature injury occurs when temperatures are below normal and also when winter temperatures rise, breaking plant dormancy, and then return to winter temperatures injuring soft plant tissue. The low temperature injury after plants break dormancy can also be attributed to a late frost and can occur from now through spring. Damage to plant tissue results in bud or branch mortality, leaf out and then collapse, and delayed leaf development of older branches.
1) Select cultivars of trees and shrubs that are hardy in your area. Quality nurseries and landscapers carry trees and shrubs that are cold-hardy in the mid-south climate and inform customers of any landscape plants that are susceptible to low temperatures or that should be treated as annuals.
2) Avoid high nitrogen fertilizers in late summer/early fall. High nitrogen fertilizers can force new growth creating tender shoots susceptible to low temperatures. Late season fertilization should have a low ratio of slow release nitrogen fertilizer to prepare the plants and its roots for the dormant season.
3) Water trees and shrubs appropriately during the summer and throughout the fall and winter if the soil is dry. Trees and shrubs withstand low temperatures much better if soil moisture is adequate. A 2-3” layer of mulch will conserve soil moisture and help protect the root system from winter damage.
Dormant trees and shrubs, and especially evergreens, continue to lose moisture even in the coldest winter periods. The rate of water loss increases with fluctuating temperatures, drying winds, and full sunlight. Trees and shrubs, planted in low quality upland soils that are not holding soil moisture and that are exposed to harsh winds, are particularly susceptible to winter desiccation. Damage appears as brown needles and leaves (especially on the windward side) on evergreens and dry and brittle branches that do not leaf out on deciduous plants.
Winter desiccation injury can be prevented by proper watering and mulching as mentioned above for low temperature injury. For high value specimen plants, screens of burlap, plastic, or wood can be placed around the plant to protect it from drying winter winds.
Trees and shrubs that have sustained winter injuries will need corrective actions to help the plant recover. Dead or damaged limbs should be correctively cut and trimmed to help close wounds and prevent spreading decay. Injured plants should also be fertilized to help recover and grow new tissue around sunscald injuries or damaged limbs. Trimming and fertilizing will correct the initial injury, maintain plant vigor, and will also prevent trees and shrubs from becoming susceptible to insect, disease, and environmental issues throughout growing season.
If you would like to speak with one of our arborist concerning winter injuries to trees and shrubs or other tree related issues, please call (901) 309-6779 or email us at firstname.lastname@example.org and set a meeting with our arborists today.