Plants influenced by growing media and compost addition on mock green roofs within the ozark highlands

Green roof technology and other low impact development practices help mitigate hydrologic impacts from urbanization. Green roofs are widely recognized for stormwater retention, and these systems provide many other ecological functions, such as habitat, air quality improvements, insulation, reduced noise pollution and aesthetic quality. Green roofs are composed of a plant palette (species selected for a specific condition), growing media and drainage system on top of a traditional roof membrane. This study investigated species survival under local environmental conditions, in the southwestern Ozark Highlands from September 2008 through 2009. There were four treatments consisting of two different growing media particle sizes and two different fertilization regimens (with and without compost). Sixteen plant species and/or varieties were monitored to determine the effect of treatments on survival and spread. Plant response varied by species, but the fine media with compost provided the greatest survival and spread. However, the fine media without compost treatment had similar survival rates and may provide similar cover over time. The coarse particle media treatments had greater mortality rates in most specimens and less coverage after one year. Local environmental conditions were detrimental to some species (Sedum moranense L.), whereas other species (Sedum reflexum L.; Phedimus sp. L.; and Sedum spurium L. 'Summer Glory') thrived. Our results provide valuable knowledge on creating an appropriate plant palette for green roof designs.