Growing Large, Healthy Urban Trees

While mature trees can contribute significantly to stormwater treatment, successfully growing large trees is especially challenging in urban environments, precisely where their stormwater services are most needed. To determine how best to address this problem, a study by Bartlett Tree Research Laboratories has been investigating and comparing different techniques to extend uncompacted soil rooting volume under pavements since 2004. The study compares structural soil, expanded slate structural soil, expanded slate, and suspended pavement. Seven years into the study, results show that trees grow best with suspended pavement. To investigate how to address concerns that tree roots will crack or lift sidewalk pavement, creating a tripping hazard for pedestrians, another study by Bartlett compared several methods to reduce pavement damage from tree roots. The study found that pavement damage from tree roots can be greatly reduced with effective along-side pavement vertical barrier treatments.