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. 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 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.
Roots are damage in many ways. The first is soil compaction. This damages feeder roots limiting the nutrient and water-absorbing capacity of a tree. Symptoms of soil compaction appear in the tree canopy as unhealthy foliage, yellowing, and branch dieback. Compaction of the soil is common in construction projects due to heavy construction equipment. One way of protecting trees during the construction process is placing protective fencing around the dripline of the tree’s canopy.
A second problem for roots is changing the soil depth. Avoid placing soil on top of the roots. If root depth increases by as little as 2 to 4 inches, oxygen and water availability is significantly affected.
Lastly, improper watering, both under- and over watering, leads to an unhealthy root system. Over watering reduces oxygen and under watering leads to poor root growth. As you can see, any change in soil condition, water supply, or oxygen supply can be very detrimental to the tree. Healthy roots means healthy tree.