Root Collar Excavation
Buried root collars is one of the most common and consequential issues in urban trees. It alters root development, increases the risk of girdling roots, and can silently shorten tree lifespan. Root collar excavation is a key tool for diagnosing and correcting this foundational structural defect.
Research Summary
Richard G. Rathjens, T. Davis Sydnor, and David S. Gardner
The article “Evaluating Root Crown Excavation as a Treatment for Deeply-Planted Landscape Trees” (Rathjens, Sydnor & Gardner, Arboriculture & Urban Forestry, Vol. 35) evaluates root collar excavation as a corrective practice for trees suffering from deep planting and buried root flares.
Across multiple field sites and species, the researchers found that root collar excavation reliably exposes the root flare and frequently reveals hidden girdling roots—confirming its importance as a diagnostic step for correcting long-term structural defects in urban trees.
The key implication is that the long-term value of root collar excavation is not immediate “revitalization,” but rather restoring correct root architecture and preventing progressive decline caused by buried root collars and girdling roots. By re-establishing the proper position of the root flare, root collar excavation helps reduce ongoing structural stress, improves conditions for oxygen exchange at the root crown, and allows arborists to address hidden defects that would otherwise continue to worsen over time.
Research Summary
Susan D. Day Gary Watson P. Eric Wiseman and J. Roger Harris
The article Causes and Consequences of Deep Structural Roots in Urban Trees: From Nursery Production to Landscape Establishment synthesizes research on how and why trees end up with structural roots buried too deeply, and what that means for long-term urban tree performance.
A central finding is that deep structural roots are extremely common and can originate at multiple stages—nursery production, transplanting, or later soil deposition in the landscape. These practices often lead to root collars being buried, which alters root architecture and the development of the root flare.
Deep structural roots are linked to important long-term risks, especially the development of girdling roots, where roots grow in tight contact with or around the trunk, potentially restricting vascular function.