Kelly Jackson
Christian County Extension Office
Magnolia Leaves Showing Winter Burn
Evergreen trees and shrubs may have been injured this winter to the point that many are showing signs of winter burn. Arborvitae, cedar, pine, yew, boxwood, rhododendron and magnolia are among a few likely to be exhibiting symptoms now and into the spring.
Winter burn is an environmental injury that occurs when needled and broadleaf evergreens continue their normal plant processes through winter but are unable to replace the water transpired (lost through leaf pores) at the same rate. This can happen for several reasons. Newly established trees may lack sufficient root system to absorb enough water; the ground may remain frozen making it impossible for the plant to absorb water or there may be a lack of available soil moisture due to less rain or snowfall. These situations are compounded when evergreens are exposed to direct sunlight, reflected sunlight or windy conditions. Often winter burn is most severe on the side of evergreens exposed to the sun, wind, or both.
I have noticed this is especially true of the Southern Magnolia. This tree is already at a disadvantage because Kentucky is at the northern edge of its adapted climate (Zone 6 to 10) but with winter sun exposure and wind it is almost always one of the first to show winter burn. Symptoms will appear as leaf browning and leaf drop.
Rule number one in addressing winter injury is to be patient. If the foliage or the tips have been damaged but the stems and buds are still green, wait until the plant puts out new growth before deciding if the plant should be pruned or removed. Sheering dead foliage will immediately improve the appearance of the plant, but pruning should not be done until after the chance of the last frost has passed.
Spring fertilization is not recommended, especially for plants suffering winter injury. The addition of nitrogen can encourage more growth than the damaged stems can supply with water during hot, dry summer months ahead. The addition of water during dry periods is more beneficial than the addition of fertilizer. When necessary, fertilization of woody landscape plants should occur in late fall.
Established evergreens in exposed locations can be protected from the intensity of winter sun and wind. Cover these plants with light-colored cloth or burlap prior to the onset of winter. Spray moisture on the cloth prior to the onset of extremely windy sub-freezing temperatures. Water frozen on the cloth will further reduce the effect of the wind.