Tree Root Myths
Douglas L. Airhart & Guy Zimmerman III

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        Common Tree Root Myths:  

Here’s a question: When healthy trees are up-rooted by storms, what does the root mass look like? Are they clumped at the end of the trunk like a lollipop, or are they flat and spread out from the trunk like a flat pancake? (Click here for the answer.)

The root system of trees is the key to their survival. At construction sites, protecting tree roots is the most important step to keep your remaining trees healthy. Unfortunately, most people do not understand tree biology, and may have mistaken ideas about tree growth. A few Myths That Kill Trees are:

    Myth 1: Tree roots exist only under the tree canopy, or out to the drip-line. Tree biology: tree roots, especially in forests, extend well beyond the drip-lines of the branches. Often two or three times further. During construction, keeping equipment and trucks away only from the tree trunk is not enough to prevent damage to trees. Equipment and trucks will squish the soil in the root zones.

    Myth 2: Tree roots grow deep into the soil and thus are protected. Tree biology: All roots need oxygen to survive. Heavy clay soils, and soils compacted by traffic, have little air space, so roots must stay in the upper levels to have enough air to survive. If construction traffic squishes the soil, it closes the air pores and this will cause existing roots to suffocate and die, or be damaged.

    Myth 3: Tree roots are woody and tough. Tree biology: Woody structural roots near tree trunks are tough, and they help support and anchor the tree. But the small, fleshy roots at the outer reaches of root zones gather most of the water and nutrients needed for healthy trees.

(Figure 10-1) Trenching Damage.

Excavating, topsoil removal, and trenching activities that cut roots will prevent trees from absorbing critical supplies of water and nutrients

    Myth 4: Damage to tree roots can be seen immediately. Tree biology. Trees have stored energy in their branches and trunks that they use to survive after roots are damaged. It may take two or three years for trees to begin to look like they are declining. And it may take up to five or ten years for root damage to result in tree death. By then, the building contractor is gone and no longer responsible. This visual decline is what causes tree owners to call tree companies to “save their trees”.

    Fact: Tree trunks and branches are tough. You have seen trunks with large scars from being scraped by bulldozers, and you have seen branches broken by backhoes, and the tree will survive for many years. But trees whose roots have been damaged will begin to decline in health, and may eventually die if not treated.

    Summary: A little prevention at first is the best technique to protect your trees from construction damage, and to keep your trees healthy in the future. Contact a Certified Arborist for help to protect your trees from construction damage, and to save trees that are showing signs of decline from construction activities.

Used with permission of Tennessee Tech University, (Photo courtesy of J. Plant, 2002).

(Figure 10-2) Preventing Damage.

Using durable construction material to mark the tree protection zone (partly within the drip line).


Purpose    Right Tree / Right Place    Selecting Trees    Transplanting Trees    Mulching & Staking    Summary Diagram     Pruning Trees    Topping Hurts!      Protecting Trees     Tree Root Myths     Pine Bark Beetles     Live Christmas Trees     Glossary     List of Figures    List of Video Vignettes    Related Links     Bibliography is maintained by: Douglas Airhart, Ph.D. Certified Arborist & Jeff Plant, Ph.D, Last Updated on: 07/11/03