Landscape architects are dedicated to planting trees in the city, but the contemporary city is not hospitable to healthy mature trees. In response, we rely on often-competing planting strategies and details. Rarely, however, do we analyze the relative outcomes of our choices of soils systems, pavement details, and management practices. In response, two landscape architects, an arborist, and a soils scientist joined forces to undertake a comparative study — through fieldwork and laboratory testing — of plantings that have endured the stresses of an urban environment in Boston for between 5 and 45 years. Our findings are preliminary and suggest that additional data gathering and analysis is necessary, but they do begin to shed light below the surface of the city, indicating that soils under pavement are indeed highly dynamic systems that are influenced by their context and they mature and change over time.