Have you ever seen a shade tree, let’s say between the ages of 15 and 25 years old, in the early stages of decline? Smaller leaves, fewer leaves, entire branches dying in the crown of the tree, or entire sections of trees not leafing out in the spring? Unfortunately, the number of trees exhibiting these symptoms in our home and commercial landscapes is becoming an all-too-common sight. Trees entering their prime years should not look this way. What could be going wrong?
All kinds of factors can contribute to poor health and shortened lifespans for trees. Drought stress, extremely low winter temperatures, and yes, even certain insects and diseases might be added to the list of suspects. But recently, at least over the last decade or so, a disorder called stem girdling roots (SGRs) has emerged. And unfortunately for our trees, the occurrence and prevalence of SGRs is seemingly on the rise.
What are Stem Girdling Roots?
Stem girdling roots happen when a tree’s own roots either completely encircle the trunk or grow tangential to the trunk on one or more sides, causing stem compression and damaging important vascular connections (xylem and phloem). Stem girdling roots can develop on practically any tree species but are most commonly found on maples, lindens, and elms. They are easiest to spot and treat when they form in plain sight (above ground), but more often than not, they go undetected below ground. But why would trees inflict this kind of damage on themselves?
What Causes Stem Girdling Roots?
It’s a complicated story, but we think most SGRs get their start in the tree nursery and particularly when trees are grown in smooth-walled plastic containers. Trees grown in these containers often develop a dense mass of roots that tend to spiral or circle around the inner wall of the pot. And if these root systems are not disturbed, broken apart, or otherwise “fixed” at planting time, then those small, innocuous-looking roots can, over time, become problematic stem girdling roots.
How Do I Prevent Stem Girdling Roots?
To their credit, the nursery industry has developed a new generation of containers that limit or eliminate the pot-bound, circling root problem. But unfortunately, adoption of these new and improved containers has been slow. In the meantime, it is imperative that we purchase high-quality plants, plant trees at the proper depth at planting time, address debilitating root issues that result from growing trees in pots, and, whenever possible, eliminate stem girdling roots that have developed on our landscape trees before they cause tree decline symptoms. Ignoring the problem sentences trees to an early and totally preventable demise.
How Do I Fix a Tree That Has Stem Girdling Roots?
Unfortunately, if an established tree has SGRs, nothing can be done to correct it. Cutting the offending roots visible at the surface out will only cut the tree off from a (potentially large) portion of its root system, causing even more damage. Additionally, many SGRs are located several inches below the soil surface, so finding them without destroying the tree's root system is not possible.
The only way to fix the issue of SGRs is to plant trees at the appropriate depth and remove or redirect circling roots when planting. Trees in poor health with thin crowns and dieback, those that are not structurally sound, or trees that pose a threat to people or property should they fall should be removed. A certified arborist can help you determine the health and stability of your tree.
More Information
- How to Diagnose Problems with Trees in the Landscape
- Decline of Newly Planted Trees
- Planting Trees in the Landscape
- How to Plant a Container Grown Tree (video)
- Tree Planting Basics
- How to Plant Bare Root Trees
- How to Plant a Bare Root Tree (video)
- Care of Newly-Planted Trees
- Community Tree Planting and Care Guide (publication)
- Choosing an Arborist (publication)