Hidden Dangers

What You Can’t See Can Hurt Your Trees

Excavated oak root
A tree gets the water and nutrients it needs from the roots. If a portion of the root system is severed, or the roots are otherwise compromised, the tree will suffer proportionately. As roots serve as an anchor to keep the tree upright, when there is a problem with the roots, there is also a problem with the structural stability of the tree. With roots having such vitally important duties, their management is an essential part of tree care. An “out of sight, out of mind” mentality can result in catastrophic consequences.

What’s Happening Underground?

Tree roots extend well beyond the drip line, as far as three times in some cases.

Tree roots extend well beyond the drip line, as far as three times in some cases.

Roots grow where the resources they need are located. That means most of a tree’s fine feeder roots are in the top twelve inches or so of soil. Large structural roots may grow several feet deep, depending on species and soil conditions. These large roots grow closer to the trunk of the tree with fine feeder roots extending one to two times the height of the tree.

Porous spaces in the soil allow for better root growth and subsequent absorption of water and nutrients. When the soil is compacted, these porous spaces are reduced, making it difficult for roots to extend and do their crucial work. This is a common issue on urban and suburban properties where trees coexist with people, machinery, pavement and structures. Soil compaction and inadequate aeration are the major barriers to tree growth on commercial sites, followed by improper irrigation.

The Cover Up

It’s often said that the cover-up of a mistake causes more trouble than the mistake itself. And so it is with trees. When soil or excess mulch is piled against the lower trunk and root collar areas, problems with the root system are often ‘covered up.’ Watch this video to learn how to spot a buried root collar:


The root collar is the transition area between a tree’s trunk and its roots. While roots are able to tolerate high levels of soil moisture, the above-ground root collar is not.

Excess soil hides girdling roots that slowly strangle a tree, restricting movement of water and nutrients.

When soil is up against the bark it remains damp, frequently resulting in infection by root-attacking fungi such as Phyophthora and Armillaria.

Girdling roots can also be hidden under excess soil. These lateral roots sit at or just below the soil line, pressing into the main trunk. Girdling roots should be removed, but this must be done with care to minimize injury to the trunk and impact to overall tree health.

What’s Happening Aboveground?

Even though you can’t see what’s going on with the roots of your trees, they’ll let you know a problem exists.

Symptoms of a root issue include:

  • Light green or yellowing foliage
  • Early leaf coloration
  • Upper branch dieback
  • Dark areas on trunk or buttress roots
  • Oozing liquid on trunk or buttress roots
  • Presence of mushrooms or fungal growth near the trunk
  • Poor ground cover growth under the canopy
  • Abnormal swelling of the base of the trunk

Here’s the kicker, though. Many of these symptoms may not be apparent for years after root damage occurs. That means the tree is living in a weakened state. Not only will it be more susceptible to pests and disease, it can also be more prone to failure under any conditions.

Getting to the Roots

Remember, “out of sight, out of mind” is a dangerous mentality. The best thing you can do to protect your trees is to keep roots in mind and prevent damage before it happens.

Avoid root-cutting activities, such as grade changes or installation of underground utilities, within the dripline of the tree. Also avoid piling of soil against the buttress roots and trunk of the tree. Be mindful of using deicing salt near trees and do not allow traffic in the shade of the tree such as the parking of cars.

If soil is compacted, consider options to cultivate the soil. The method we use is a supersonic air tool that tills the soil while minimizing damage to the roots. These loosened soils are then amended with organic matter and nutrients as needed to optimize the soil for root function.

Poor color and dieback in the crown result from root problems in a live oak. After Bartlett’s Root-Rx Root Invigoration using a supersonic air spade, the tree has been restored to good health and appearance. Watch this video to see how root invigoration works.

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Posted in Tree Advice, Urban Tree Care

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