Energy Daily reports that "Previous research on species that can survive and thrive on extensive green roofs has shown that succulents outperform most non-succulents."
Blue grama and hardy ice plant weathered the test best, outperforming other succulents.
The study is being conducted on the roof of the Colorado headquarters for the Environmental Protection Agency, a LEED-certified office building.
From the EPA's website:
"While installing green roofs has been gaining in popularity in temperate areas marked by relatively ample rainfall such as Europe (green roofs are particularly popular in Germany) and the Northeastern U.S., developers, architects, and building managers have much less experience installing them in places with low rainfall and the solar extremes presented by high altitudes. EPA's green roof is the first of its kind in the state of Colorado."