Cold Tolerance Assessment of Sedum Species for Shallow-Extensive Green Roof System

Abstract

This study was carried out to suggest an experimental base for selecting evergreen groundcover plants which can adapt well to the environmental condition of shallow-extensive green roof system by evaluating cold tolerance of seven Sedum species: Sedum acre, S. album, S. oryzifolium, S. reflexum, S. rupestre, S. sexangulare, and S. spurium. The cold tolerance of the plants subjected to laboratory low temperature treatments was evaluated using both electrolyte leakage and regrowth test, which was compared to electrolyte leakage responses of the plants exposed to on-site temperatures in a shallow-extensive green roof system. The lethal temperatures at the inflection points of sigmoidal Curves fitted through electrolyte leakage were predicted with the range of -19.9 degrees C to -27.2 degrees C indicating that S. rupestre and S. sexangulare were more tolerant of low temperature while S. spurium and S. oryzifolium were less tolerant. These results were consistent with those from the regrowth test though the cold tolerance tested by electrolyte leakage evaluation tended to be rather overestimated. At the lowest on-site temperature recorded in December 2003 to January 2004 (-9.8 degrees C) electrolyte leakage values of the plants except S. oryzifolium were lower than 50% demonstrating that they Could be applied stably to green roof system installed in South Korea during the winter.