From the Vine: Tree Decline

— Written By and last updated by Patricia Burch
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Have you noticed any of your ornamental trees or shrubs beginning to decline recently? If not, you are one of the few in Sampson County and southeast NC that isn’t experiencing this new-found occurrence. Affected tree and shrub species include dogwood, maple, oak, poplar, ornamental fruit trees, spruce, cherry laurel, boxwoods, and others. Symptoms begin with leaves wilting, turning brown and dropping off the plant, followed by tip die back, branch die back, and eventually tree death. Everyone wants to know what to spray for this disease, but is it really a disease?

From my observations, I am not finding disease, but rather damaged and/or reduced root systems which are causing the decline of all these trees and shrubs. You can point the finger of blame at Hurricane Florence, which dumped upwards of 30” of rain in our area in the fall of 2018. We were also inundated with a wet winter and received a year’s worth of rain during the winter months. Flooding, standing water, or saturated ground brought on by the extreme weather damaged many of these root systems.

Trees root systems are made up of both major lateral roots that are woody and form the support system of the tree and fine roots that are non-woody and are involved in absorption of water and nutrients to support the trees life functions. Flooding can cause damage to tree roots in several ways, but saturated or flooded soils are usually the main cause of the damage brought on by the lack of oxygen in the soil. Roots require oxygen to carry out cell functions and they get their oxygen through absorption of oxygen from small air spaces in the soil. The lack of oxygen in the soil leads to death and decay of the roots that are utilized in absorbing water and nutrients, resulting in a loss of root mass. Even if the water wasn’t standing above ground, doesn’t mean that the water didn’t “stand” below ground. Depending on how long the soil was inundated with water, tree root damage can be extensive. Stagnant water can be worse on tree roots than flowing water, since stagnant water is often depleted of oxygen.

According to the NC State University Area Forestry Agent, Colby Lambert, when the tree experiences flooding, and its root mass is reduced in size due to death and decay, it becomes more susceptible to other issues such as the abnormally dry or moderate drought conditions that we have experienced over the past few months. So, the decline we are seeing in these tree species now are likely the result of the impact flooding had on the root system and the added stress brought on by the lack of water under the more current dry conditions experienced during May through July.

Trees need water just like us, and the lack of a root system to obtain adequate amount of water from the soil ultimately can lead to the trees decline and death.

Trying to save these trees or shrubs will be a difficult and arduous task. After many hours of hard work and TLC, you may still lose your beloved plants. However, the general recommendation to try and save trees that are under this type of stress is to prune out all dead limbs and reduce the tree or shrub canopy now. Take a soil sample and send for analysis. Before the first frost, prune out any new growth that may have occurred to prevent winter injury. During the dormant season, prune the tree or shrub back to the natural shape. In the spring, follow the recommendations for fertilization and lime as recommended by the soil analysis.