By: Anthony C. Arnoldi, Certified Arborist
As the root system goes, so goes the health of the tree.” This old adage that many plantsmen of yore lived by, has its basis in strong factual science. This is why a transplanted tree will spend 5 years desperately trying to replace its root system FIRST. A tree will die if there is not a sufficient root system to support its growing top.
But that is the very scenario that plagues urban trees: insufficient root systems. Under the influences of turfgrass, compacted soil, high soil temperature, greatly diminished average soil moisture, thin or non-existent top soil layer, and perhaps most important: few to no root associates. This article will reveal the identity and the importance of the root associates and how they can be used to improve tree health.
In nature, roots grow in what is called the rhizosphere. This is a thin mantle of very complex molecules and living beneficial soil organisms like bacteria, certain fungi, protozoa and nematodes, that surround each root hair. These all interact with the root and soil particles to form a critically important, mutually beneficial environment that protects, feeds, and nurtures all components of the rhizosphere, including the tree rootlets. These associates combine to work together, feeding each other in a complex “food web.” Root associates (aka: much of the rhizosphere) are mostly missing in the urban soil/ root environment. They simply can’t survive without the thick, rich forest floor. Adding forest floor material usually isn’t an option for most urban trees. However, there is a way to manage this root environment—to bring more components of the rhizosphere “back on line” to help your tree’s roots.
The first thing to do is to create a grassless, organic mulch area around the tree. Ideally, this would occupy the entire “drip line” area of the tree. Slowly decomposing mulch mimics some of the beneficial decomposition that happens in the forest floor. Humus that is created from composted organic material (like mulch) is “liquid gold” and feeds much of the rhizosphere. Roots benefit from humus— the more the better. Specially prepared humates, soil organisms and organically derived rooting hormones (collectively known as root biostimulants) can be injected into the rootzone, restoring and feeding the rhizosphere and thus benefiting the root system. Root system gains are the result with increased tree health.
Another major component to the rhizosphere are beneficial mycorrhizal fungi. These fungi are normally plentiful in forest soils and form a mutually beneficial symbiotic relationship with the tree roots, effectively forming a “secondary root system.” They account for most of a normal (forest tree) root system’s absorptive capability. They are, however, nearly lacking in most urban root environments, and stressed trees are the consequence.
Special mycorrhizae can be injected into the root zone. These are mycorrhizae that have been developed and selected for superior beneficial effect and ability to endure hostile root environments for some time. Their added presence enables a root system to function at many times its previous capacity. This is a very useful tool for managing declining or stressed trees.
Call your Wachtel Certified Arborist for an expert evaluation of your trees to see how improving the root system leads to healthier, more durable and beautiful trees.
© Copyright 2003 – Wachtel Tree Science & Service, Inc.