Root Growth of Accolade™ Elm in Structural Soil Under Porous and Nonporous Asphalt After Twelve Years

Accolade™ Elm trees were planted in CU Structural Soil® overlaid with porous or nonporous asphalt in 2005. At three separate points (2012, 2015, and 2016) over the last twelve years, root densities were measured with Ground Penetrating Radar to a depth of 30 inches (76.2 cm) beneath the asphalt. Roots under the porous asphalt were more numerous and tended to grow deeper in the structural soil profile. Shoot growth was reduced in trees that grew under the nonporous asphalt beginning in the eighth year after planting. CU Structural Soil® is a viable medium for tree growth and stormwater capture when paved with porous asphalt.