Tree roots are arguably the most important part of a tree as the tree gains nutrients, oxygen, and water from its roots and healthy tree roots not only supply these health-giving components, but also supply strength and stability for the tree. When tree roots are unhealthy, tree and/or branch failure may occur. The potential for tree damage failure is also increased when tree roots are severed or cut. Severing roots, even a couple of feet away from a tree, can severely damage its nutrient uptake, as well as its stability system, which may create a hazard.

Root Structure

The structure of a tree root system is comprised of large perennial roots and smaller, shorter-lived feeder roots. Perennial tree roots are woody and grow horizontally, primarily in the top 6 to 24 inches of soil. Rarely do they grow deeper than 3 to 7 feet. These roots anchor the tree, store food and water, and conduct water and nutrients into the tree. Feeder roots are significantly smaller, usually only 1/16th in diameter, but make up the majority of the root system’s surface area. Because feeder roots do most of the water and mineral absorption, these roots grow predominantly upward and outward from the large perennial roots near the soil surface. Feeder roots die and are replaced regularly. Typically, the entire root system of large and small roots occupy an area underground that is two to four times the diameter of the tree’s crown.

Development and Growth

Although tree roots grow mostly at the soil surface where nutrients, oxygen, and water are available, many times when a seedling is first getting established a taproot is extended deeper into the soil to ensure that the root system doesn’t dry out. Soil conditions also affect the growth and development of the root system. Soils that are compacted have fewer nutrients and less water than uncompacted soils. Soil compaction occurs naturally at greater depth, which also reduces the availability of water, nutrients, and oxygen. If soil compaction occurs at the surface, root growth is restricted.

Root Problems

There are many ways that roots develop problems, which may be avoided or mitigated with proper care. One of the most damaging of problems is soil compaction. Soil compaction leads to a reduction of oxygen and water availability and is frequently associated with construction equipment, parking lots, roads, etc. Another problem for roots is a change in soil depth. If root depth increases by as little as 4 to 6 inches, oxygen and water availability is significantly affected. If soil depth is decreased and roots are exposed, water availability is again reduced – and roots are exposed to injury without the soil buffer. Improper watering, both under- and overwatering, also leads to an unhealthy root system. Overwatering reduces oxygen and underwatering leads to poor root growth. Root systems with girdling roots or that have insufficient room to grow also develops problems. As you can see, any change in soil condition, water supply, or oxygen supply can be very detrimental.

Tree Damage and Disease Symptoms

The Morton Arboretum states that over 80% of all landscape problems originate underground. With this in mind, it is safe to say that root problems become tree problems, including limb and tree failure. Trees are stressed due to improper watering, soil compaction, change in soil depth, and injury, and any of these stresses can lead to disease and insect susceptibility. Fungi attack tree roots. When large perennial roots are attacked, growth is suppressed, structural support and food storage is reduced, and food-transporting cells decay. When feeder roots are attacked the nutrient- and water-absorbing capability is reduced. Symptoms of dead roots and the reduction of water and nutrient uptake appear in the tree canopy as unhealthy foliage – such as yellowing, scorching, and dieback. Fungal growth may appear at the base of the tree as well as under the bark. Insects attack in three ways – chewing, sucking, or boring. Chewing and sucking insects affect leaves, and this reduces food production; boring insects disrupt the transfer of water and nutrients.


To prevent root problems, which lead to whole tree problems, keep soil from being compacted, ensure adequate soil depth, adequate water and nutrient supply, and adequate space for roots to grow.

Evergreen Arborist Consultants, Inc., is a tree root specialist

for the Los Angeles, San Francisco, Orange County, and San Diego Areas. We provide expert witness and litigation support for construction defect, tree root damage cases resulting from severed tree roots, and roots that cause damage to infrastructure such as sidewalks, foundations, and sewer pipes. We also provide consultations for cutting tree roots.  Call or email us today.