Dobe on a branch


Root Crown Excavation

When I first created this website, I had no idea that the article I wrote about soil levels for trees would receive so much attention. I get calls and emails from people in all the other states, to say nothing of the people here in Austin, Texas. To be sure, the problems the trees have with soil level and mulch is widespread. I seldom examine a property that does not have trees that have their root crowns under soil or mulch. It stands to reason, therefore, that information about this problem would receive a lot of attention.

I have, therefore, come to the conclusion that the issue deserves more explanation and this article and others is the result. I took some photographs and prepared them for posting here that should be helpful I must say, it is not easy to create a website with photographs and text to explain them. I spent a lot of time reading books and practicing. So, please be lenient with my work. I do the best I can.

What Happens When the Soil is Too High on a Tree Trunk

Things go wrong when the bark of a tree get covered. Anything that covers "bark" is going to cause the tree to have problems, but you may be unable to detect them until the problems have been developing over a long period of time, perhaps even decades. Being unable to detect problem does not mean they are not there. If you cannot see the root crown of your tree, something is wrong. You can see the root crown pictures on another page of this site titled Soil Level For Trees. Of course, you can just click the words in the previous sentence. The things that go wrong for the trees varies by species, individuals, location, season, previous condition, and more. I have said it before, nothing can be written in stone about trees. Each tree is unique and requires unique understanding and treatment. The need for an arborist is expressed by this fact. First, I want to show you what is exposed by excavating a root crown.

Tree with soil removed from around the baseThis is a picture of a post oak that has had some of the high soil removed. You can see that the bark is stained and smoothed. There is still a lot of soil to be removed and the owner of the tree is going to do so. This tree was not looking well. It had a low leaf count, limbs were dying, and it looked stressed in general.

I have seen remarkable results obtained by this simple chore of removing the soil that has gotten so high that it covers the bark of the root crown and the trunk. The trees seem to get a new lease on life and begin to produce more leaves. They enjoy other benefits, too, that are not visible, such as: increased resistance to pests and diseases, better root development which also improves the tree's anchorage in the Earth, and better water and nutrient flow. It just makes the trees come back to life. The tree at my home was suffering the same problem when I bought the place and excavating the root crown cured its problems.

In the next photograph you can see how some examples of the live oak species respond to high soil and bark burial. This does not happen to all live oaks. I do not know why it only occurs on some. The seven hundred year old live oak in my yard did not develop the adventitious root development that you can see in this picture. Of course, when the tree does not develop the extra roots, it is much easier to remove the soil that is too high on the root crown and trunk. The root mass that grows into the new layer of soil makes removing the high soil nearly impossible. In some cases it just can't be done and the poor tree is just going to have to deal with as best it can.

Bear in mind that roots grow constantly. They increase in number, diameter, and length. As this happens, especially in cases such as the one pictured, they begin to crowd one another and even merge into one. As the roots press against one another with greater force as they grow, they begin to weld themselves into on woody mass. I think of it as a woody, tumorous growth. The process is a way for the life of the tree to be preserved. As you can see on the other page about soil level that shows the baby live oak leaves, new trunks are growing from the woody root mass. When the main trunk decays through and dies, the tree will have a new set of stems that have changed root systems to accommodate the new soil level. It is, as I have said, a survival technique some of the live oaks have. I know of no other species that does this. Some send roots away from the trunk and new stems grow from them. The Gum Bumelia does so rather well, as does the pyracantha This, however, is not the same as what you see in this picture.

Excess root mass  in the high soil around the trunkThis tree has developed so much root mass in the high soil, it is not possible to remove it all enough to solve the problem. It will have a better chance of living longer by removing what can be removed, but it can never be the same tree it was born to be.

In the next photograph you will see examples of what can be done after the root crown and trunk have been excavated. We call this construct a "root well."

Root wells can be constructed in almost infinite variety. The look and style is really a matter of taste and available funds. If a root well is not installed, the depression around the tree will still accomplish the desired results, but the the depression will eventually become filled and require help again.

One thing that can be a great addition to the root well is drainage. To prevent the root well from becoming full of soil and requiring more frequent maintenance, install a drain.

Rock laid around a tree trunk that has had the soil level restored to a lower levelTo drain a root well is a matter that must be done in relation to the situation at hand. On inclined areas, the down-hill side of the root well can be left open allowing erosion to keep the soil from accumulating. In flat areas, a drain pipe with a grill over the opening can be installed. Of course, the pipe will have to be installed with a grade down hill and an opening into an area that can take the flow of water.

This root well in this picture is not done well enough, but you can see what one looks like. The soil in the bottom of this root well is still too high and there is no evidence of a drain. Without the drain, and sometimes even with a drain, maintenance is required. Soil that accreats around the trunk will have to be removed from time to time to maintain the proper soil level. There is not getting around the fact that what has happened to the tree is going to be source of time, energy, and even money requirements. The alternative is the death of the tree.

Let me make sure you understand the time element in the process of dying due to hight soil levels. Aside from the adventitious root mass that grown around some live oaks, what happens is the decay of the bark and the killing of the cambium around the trunk. It is not a fast process, so don't panic when you discover that the soil is too high for you trees. It can take fifty years for some trees to die from this problem. In other cases it may be as little as a few years, but unless you are already seeing your tree has too few leaves and you have found that the soil has been too hight for a long time already, there is usually plenty of time to get the excavation done. The sooner the better, but there is no reason to panic as I have seen some people do.

One of the phases of a tree's decline from high soil is the loss of foliage and limbs. I have my own theory about this. Trees don't have hearts like we do to pump fluids around. The mechanism for transport of fluids is a biologically enhanced system of osmosis. Remember osmosis? Put a sponge in water and the water will enter the sponge by means of osmosis. The pressure differential is what makes osmosis. The trees roots are in the ground where the water pressure on them is high. The leaves are in the air and the light where the pressure is low. This is an over-simplification, but it makes it easy to understand. The high pressure moves the water to the leaves where the pressure is low. The biology of the vascular system of the tree makes this simple process function adequately to meet the needs of the tree.

The veins and arteries we have are sort of parallel to the vascular system of a tree. They have xylem and phloem. The phloem takes the products of the photosynthesis going on in the leaves and transports it down to the roots and other parts of the tree. The xylem take the moisture and nutrients from the roots to the other parts of the tree. The phloem is just beneath the bark, whereas the xylem is deeper in the wood. When the high soil keeps the bark moist too long, the first part of the tree's system to feel the damage is the phloem. Thereby, the tree's root system and becomes deprived of the essentials needed to live and begin to decline. Subsequently, the canopy of the tree begins to decline. It has fewer and fewer leaves over time and limbs begin to die. Ultimately, the tree dies, unless it has a survival stem somewhere to carry-on the life of the tree.