Tree Care Starts on the Ground
The importance of protecting the root system of a mature tree cannot be overstated if the long term health of a tree is important. But what exactly do we mean by “protecting the root system?” We will get to that later into the column but first try to visualize this word picture as it is important in understanding how much root protection is enough.
Many of us are under the impression that if you pulled a tree out of the ground with its root system intact, the roots would be a mirror image of the top growth. This is untrue. A better model would be to turn a dinner plate upside down and place a wine glass on it. The goblet bowl would represent the leaf canopy, the stem would be the trunk, the base would be the critical root flare, and the dinner plate would represent the feeder roots.
With this image in mind, you can see that feeder roots extend out well beyond the dripline of the tree, often times 3 to 5 times the distance of the tree itself. It is these roots that the tree depends on for nutrient and moisture intact and air exchange. When they are damaged or covered, the tree will suffer to some extent. Just how much of this damage a tree can take is highly variable and is dependent on several factors including species, soil conditions, environmental conditions and sudden changes to the microclimate.
The root flare, the area above ground where the tree begins to widen as well as the large structural roots immediately below ground, is even more important to the long term health of the tree. This area should be protected completely if at all possible.
What exactly is meant by protection? Basically, it is anything that might dramatically alter the soil where these roots live and work to sustain the tree. This could be as non-invasive as soil compaction. A classic example of this is when areas under trees suddenly become regular parking areas, or in the case of housing construction, material staging or storage areas.
Adding soil to an existing area is also discouraged. While the problem may appear to be different from compaction, the net result is the same. Air and water movement is suddenly limited by the change.
Moving on to a more extreme example would be destroying the roots by deep rototilling or soil removal. During the drought of the last few years, I saw several examples where trees finally gave up and died when unknowing homeowners rototilled under their trees attempting to re-establish their lawn. The loss of the root mass was simply too much for the stressed tree to overcome.
Does this mean that if you’ve done some of this to your trees that they are going to die soon? Not necessarily. As an Extension Educator, clients often dislike hearing the words “it depends,” but that is exactly the case here. As already stated, a trees ability to withstand damage is dependent on many factors. All I can say with certainty is your trees will be much better off if the root zone is not damaged in the first place since once it occurs, there is not much that can be done to compensate for it.
For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at firstname.lastname@example.org, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.
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