Species selection and stormwater runoff analysis from greenroof systems

Greenroof systems have several well identified benefits to building owners as well as municipalities. However, the use of greenroof technology is relatively uncommon in the United States compared to many European countries. Several obstacles must be overcome if greenroof technology is to be widely implemented across the U.S. One of these obstacles is identifying what specific species will survive under harsh rooftop conditions and specific climate regions of the U.S. Simulated rooftop platforms were constructed to evaluate several species of Sedum and plants native to Michigan using three commercially available drainage systems. Runoff volume was measured and analyzed for nitrogen and phosphorus contamination. Two Sedum and six Michigan native species were used to evaluate the affect of incorporating increasing levels of PermaTill® (60, 70, 80, 90, and 100%) into the growing substrate. Three native and two Sedum species were also used to evaluate plant establishment and growth using increasing levels of controlled-release fertilizer (0g·m−2, 50g·m−2, 100g·m−2, and 150g·m−2). Differences in drainage system design had no effect on plant establishment and growth, but were a factor in runoff quantity and quality. Substrate containing as much as 80% PermaTill ® and a fertilizer level of 50g·m−2 were found to maintain adequate plant health.