Gary Johnson, Professor, Urban and Community Forestry, Department of Forest Resources, St. Paul, MN; Dennis Fallon, Vegetation Management Coordinator, Xcel Energy; Andrew Rose, Creative Director, Hand/Eye Communications.
How many trees die prematurely each year? Thousands? Millions? Billions? It’s almost impossible to pinpoint, but one unseen culprit – dysfunctional (abnormal) root systems – is responsible for an inordinate number of tree failures. It is estimated that one-third to one-half of tree losses during windstorms may be attributed to distorted and dysfunctional roots (University of Minnesota data, 1995-2005).
A stem girdling root is a type of dysfunctional root that is growing against a tree’s stem (the trunk), squeezing or compressing the sapwood. This happens as the root and stem grow radially (enlarge in diameter) and eventually this compression may severely retard or stop the flow of water, nutrients and sap (photosynthates, a.k.a., “food”), both to and from the roots.
This booklet discusses the issue of stem girdling roots, specifically addressing the following topics:
- Are stem girdling roots a problem?
- What do stem girdling roots look like?
- Stem girdling root diagnosis: Above ground symptoms
- How do stem girdling roots form?
- Root collar inspections
- Prevention, treatment & recovery
- Additional resources about SGRs