Evaluating Root Crown Excavation as a Treatment for Deeply-Planted Landscape Trees

Abstract

An experiment was conducted over a four-year period to evaluate root crown excavation (RCE) as a treatment for deeply-planted landscape trees. Tree growth, leaf chlorophyll, stress, and pest activity were monitored to determine plant response to RCE. Four of the sites, including shingle oak (Quercus imbricaria Michx.) street median strip trees, blue spruce (Picea pungens Engelm.) park trees, and honeylocust (Gleditsia triacanthos L. var. inermis (L.) Zab.) parking lot island and street trees failed to show any influence of RCE on tree growth and leaf chlorophyll. Two sites with maple (Acer spp.) park and street trees where RCE included removal of potential girdling roots resulted in a detrimental effect on twig extension and leaf chlorophyll. Measurements of chlorophyll on ash (Fraxinus spp.) park trees, and tree height and twig extension on lacebark elm (Ulmus parvifolia Jacq.) street trees, demonstrated a positive influence of RCE. The RCE treatment did not influence stress or pest activity at any of the experimental sites. Since tree disorders frequently require many years to develop it is speculated that a longer observation period may be necessary to see a greater impact of RCE on plant growth and health.