The Tree Tender
Austin Area Tree Care Tree Service
by highly trained professionals. Certified Arborist.
Nickey Bishop provides loving care when pruning, trimming, cabling, and caring for trees.

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Mulch

    This is a subject of much interest to me. There is a conflict of interest going on concerning mulch. Landscapers, and sometime homeowners, feel it is a good idea to make rings around the trunks of trees by removing the grass and then covering the bare soil with mulch. Sometimes the soil around the trunk will be cultivated and flowers will be planted there. These two practices are not good for the trees, but it can even be worse.  I was called out to work on the trees at a man's house. My initial inspection revealed live oak trees that had over two feet deep flower beds built around them. The beds were contained by expensive rock walls over two feet high that were mounted on footers dug into the ground. I am afraid my advice to the homeowner made someone angry. I got a nasty anonymous message a couple days later. The homeowner had spent a lot of money to make his property more beautiful. The landscaper was probably happy to get the job. I made sure the owner of the trees knew that his trees would die because of the flower beds. My job is taking care of trees, even when someone else doesn't like me for doing it.

    Using mulch around trees is a practice that is far to common. I am not sure how this practice got started. My guess is that it comes from the practice seen when trees are transplanted. In any case, it is not a good idea to put mulch around the trunks of  trees, and that includes transplanted trees
 ( Transplanting trees is dealt with on another page). There are several factors involved, and I will address these factors in the following text. For now, I want to work on getting this practice discontinued. Spread the word! I am constantly having to deal with this issue when I am out in the field. Everywhere I go I see mulch rings around the trunks of trees. When I see this it makes me wonder why the property owner is trying to torture the trees to death. Of course, the answer is obvious. The people know not what they do.

    A tree that is established, (the roots are in the native soil), does not have the ability to absorb nutrients and moisture in the area right around the trunk. The roots that feed and drink are further out, under the limbs. The area near the trunk needs to be kept dry and clean because that is the area of the root system and trunk that supports tremendous amounts of weight and stress. Any thing that weakens the tree in that area must be avoided. If you gently dig away a small area of soil from next to a tree trunk you will see many forms of life. These life forms are finding shelter and sustenance there. Many of these life forms would love to get access to the tree's internal systems and they are ever vigilant for an opportunity to do just that. Moisture aids their cause. Mulch, therefore, aids their cause. Decay is promoted by moisture caused by mulch. It just is not a good idea to put a mulch ring around the trunk of a tree. 

     Trees in Central Texas have adapted to the weather that was the average weather of the past millions of years. That means they do not like lots of moisture. Austin, is (or I should say "was") in the northern most border of the northern sub-tropical zone of the continent. This sounds like we get rain that is a little tropical. The fact is that our average rainfall has been about 32 inches per year for a long, long time. The critical factor, though, is that the rain came mostly in huge downpours a few times a year. That coupled with the sparse soil and awesome drainage has meant low moisture for trees and low moisture near the trunks of trees. It also has caused the trees to be very drought tolerant. Six months without a drop of rain in the Austin area causes very little tree death. On the other hand, rain every day would eventually destroy most of the native vegetation around here, including trees. So, why the rush to mulch trees in yards, even yards with built-in irrigation systems (sprinklers for lawns)? I have removed many very old dead cedar (Ash Juniper) trees from landscaped and irrigated lawns. One man had expensive consultants from A&M come to save a dying cedar tree. They offered no suggestions. Perhaps they did not see the sprinkler head near the trunk that was keeping the beautiful grass alive. This grass was put in on top of a clay containing base. The grass came as "sod". Sod has a rich layer of soil with it. The poor old cedar tree that the homeowner loved was killed by too much moisture. He didn't discover The Tree Tender until he searched for a tree service to remove a dead tree. I saved the huge cedar trunk of that tree. I still have it and hope to make something from it. It is a beautiful column of cedar wood over two feet wide at the base, nearly two feet wide at the top, and about fifteen feet long. Imagine the beauty and glory of that ancient tree living long enough to get that big only to be destroyed by over watering. The tree might have survived the watering had it not been for the extra soil and sod acting as a moisture retainer (mulch). You can learn about watering trees by clicking on this link: Watering. What I want to do now, though, is continue with this subject, especially as it relates to "soil level."

    Mulch causes more problems than those derived from excess moisture. Of critical importance to the trees in the Austin area is the fact that the mulch almost always raises the soil level at the base of the trunk. The live oaks of Central Texas do not respond favorably to this condition. I have to cope with the trouble caused by elevated soil levels far too often. It is a daily occurrence. The problem is compound and difficult to explain in writing. I will make the effort. First, we need to understand that trees come with their soil level built into the DNA, it is a genetically pre-determined soil level. Deviations in the level of the soil near a tree trunk have various effects on any given species and the effects vary within the species. Our live oaks can tolerate lowered soil levels, but they cannot long tolerate raised soil levels. None of the other trees in our area can tolerate the elevated soil level, but they respond differently. The picture below is an example of how live oaks respond to raised soil level. I took the picture myself. It is an Austin live oak.

This picture shows the base of a large live oak surrounded by young live oak leaves. The leaves have small thorns along the edges (margins) something like those found on holly leaves. This is a form of protection for young live oak leaves. New roots grew from the trunk of the tree to take advantage of raised soil. The roots then send stems into the air where they grow leaves to take advantage of the sunlight. As the roots increase in diameter every year they get closer and closer together because their position does not change, only the diameter changes. Soon enough they start to touch and merge. Something like welding takes place which results in thicker and thicker diameter of roots. Eventually they will look more like solid sheet of wood. From the bottoms of these masses of roots sinker roots will grow. The sinker roots go down into the Earth and inevitably encounter the older, larger, better roots of the tree. The result is a mass of well anchored wood that interferes with the vital root system of the tree. This mass is dangerous to the tree and can result in damage to the tree and even death. This is caused by "girdling" of the tree's essential roots. It works much like a rubber band works when put tightly around a person's arm. It cuts off the circulation. Trees have a circulatory system and pressure around the root, trunk, or limb interferes with the system. When enough roots become girdled, the canopy of the tree will begin to die appearing much like it would if it were starving. The only cure I know is to excise the adscititious roots, a difficult to impossible procedure. This condition is so common I am compelled to dedicate myself to educating the public and cope with the problem wherever I encounter it.

I have drawn some pictures to help you understand the problem. I hope they will help explain the problem as it exists with live oaks. You need to understand also that even though this reaction to elevated soil levels is typical of live oaks, soil level is also vital to all trees. Keep in mind that the soil level is a genetically determined place on the tree. It is where bark meets root covering. These are two different substances and each has its own ability to stay healthy and to tolerate various conditions. Bark is designed to protect the tree from the atmosphere and all its variables, i.e. light, water, insects, fungi, and more. Bark cannot resist moisture as well as root covering can. When bark gets covered with soil it begins to decay at different rates depending on the species of tree and the other variable such as soil type and moisture content. It weakens the bark's ability to protect the tree from all the organisms that would invade the tree's system and many of these organisms are pernicious. So, keep the soil level at the right level, which is where the bark meets the root covering. This is easily seen on most species, because the bark is so much different from the root covering. If you have trouble locating the area just make sure the soil is lower rather than higher. Roots will grow bark to protect them, but root covering cannot easily replace bark, if it can do it at all.

One of the things I want everyone to know is that a tree enters the Earth via the root crown or root  flare. This is the enlarged area above the ground. It is wider than the trunk and can be likened to a golf tee set on the Earth upside down. It is shown in the drawings. If your tree does not have a visible root flare it is buried too deep. Look for parallel side emerging from the Earth like they do on a telephone pole or a fence post. That is the sign of a buried root crown. A tree with no visible root flare needs to have the soil lowered. That means digging. The result of digging out the root crown is a root well. Imaging a tree growing in a well that is only a few inches to a few feet deep. That is what you want if the soil is too high for the tree. You can line the sides of the well with rock or brick or something else that is inert. If the well is deep and soil does not drain fast enough you can install a drain in the well.

I will be adding to this page as time becomes available.