IRRIGATION REQUIREMENTS AND PLANT SURVIVAL ON NORTHWEST GREEN ROOFS

摘要

Extensive green roof plants are required to maintain multiple functions while growing in a highly aggregate media at a depth of six or fewer inches. Maximizing these functions requires maintaining plant health in extreme environments. However, management and maintenance of green roofs is often an afterthought, rarely taking into account regional differences in climate.rnThe Pacific Northwest (PNW) climate is challenging for green roof management because plants experience cool wet conditions for much of the year yet must survive warm, nearly rainless summers. We tested how eight taxa perform under three different management regimes in the PNW: (i) non-irrigated, ii) irrigated in compliance with Portland, Oregon's floor area ratio (FAR) bonus requirement and iii) irrigated using ET and runoff measurements as tools. We also measured weed pressure across the management treatments. We selected plant taxa based on their potential functional attributes (habitat quality, aesthetic quality, stormwater management proficiency) as well as their availability through the regional nursery trade.rnPlant growth and overall plant performance varied considerably among taxa and management treatment, Weed pressure also varied across treatments. These results suggest that tailoring management more precisely to plant choices and the regional environment will improve function and reduce overall costs.