February 13, 2018
We’ve experienced some bitter cold temperatures throughout the first month of 2018, which also brought some ice and snow along with it. While driving along the Newburgh riverfront this week, I noticed several large Southern Magnolias with crispy brown leaves and very little green color left. These trees exhibited obvious winter damage due to the extreme drop in temperature and exposure to harsh winds. After we experience these types of weather extremes, we see firsthand, the effects on broadleaf evergreen trees and shrubs in the tri-state landscapes. While deciduous plants are truly dormant in the winter season, evergreen plants are still transpiring, moving water from the root system up and through the leaves. Cold and dry winds can burn the foliage on these plants, causing some of the leaves to desiccate, dry up, and drop from the plant. This is similar to summer leaf scorch, a condition that causes deciduous leaf tissue to turn crunchy brown along the edges in the late summer. In both scenarios, available water in the soil is scarce, either due to dryness or freezing, and as a result, the leaves dry out. Upon entering the winter season back in December, much of the tri-state area was experiencing a deficit in average rainfall. As we get into late winter and early spring, the damage becomes more evident. Once the plant pushes out green foliage again, it is easy to see where the damaged stems end and the live tissue begins. It is necessary to prune back these damaged stems back to the new growth and let the plants rejuvenate themselves once again. An adequate dose of granular fertilizer with a higher nitrogen ratio is best for optimal shoot growth when applied around the root zone in the spring. I recommend using turf fertilizer with nitrogen content greater than 20 to stimulate rapid new growth, such as 27-3-3 or 30-3-3, and always read the label before applying. The best defenses against these winter injuries on evergreens include watering late into fall if soils are dry, and making sure there is an adequate layer of organic mulch covering the root system. One last thorough soaking, along with mulch around the roots, will retain soil moisture and help insulate the soil around the base of the plant. These are the best cultural practices to minimize winter injury.