Do not raise beds around a tree

The Cell structure between the trunk and the underground roots is very important to the health of the tree. If this cell structure is covered by dirt it will eventually kill the tree. It will not happen right away, University studies have shown it takes ten to fifteen years. During that time period the tree will be more acceptable to frost damage, leaves will be smaller, growth will show stunting symptoms and random dead limbs will show in the canopy.

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A job I was on last week had the typical symptoms already starting to show because the home owner wanted to cover rising roots. This was the worse thing to do to the tree and half of the tree has already died back just a few years after the raised bed was put in.

This birch will be dead in a few years if this raised flower bed is not removed.

We often see people raise flower beds around a tree because the roots are starting to make it difficult to mow. The correct answer would have been to create a flower bed that starts a full foot away from the buttress roots using a shallow amount of soil composite of sand, mulch and well aged compost. The best compost and mulch to use are the natural leaves that would have fallen around the tree.

Always keep in mind that tree roots must have oxygen. Leaf compost is breaking down leaving air pockets. So whatever mulch you use around a tree should not be compacted or water saturated.

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Another common problem I see is grass being allowed to grow up around the base of the tree. We discussed earlier how this is dangerous for the tree in that lawn mowers and weed eaters can damage the area just under the bark cutting the cambium or "arteries" of the tree.

However grass creates another problem in that when the grass blade is cut off, a portion of the root of the grass dies back. This helps create a thatch layer that decays into soil. Over the years this will build up. Have you ever noticed how a older lawn will have the dirt of the grass grown up two inches above the sidewalk? It didn't start out this way. The sidewalk was probably even higher than the grass years ago, but as the grass was cut and the thatch layer of roots built up, the turf ended up inches of dirt higher. This happens with the tree base too. Grass growing up around the base will build up in the same manner until we have several inches of dirt now over the buttress roots which is starting to harm the tree.

In nature, grass and trees do not mix. Trees create a canopy and a layer of leaf drop in the fall to kill off grass and competing plants under the tree. The best way to keep a tree healthy is to mirror nature. Create a large natural tree well, if possible the size of the drip line, so the tree has an area for it to grow naturally.