Considering a green roof substrate for northern climates
Twenty two substrates were developed and tested for two different green roof plant production methodologies. Growth rate analysis of Sedum sp. revealed distinct differences in performance of the mat substrates across a two year time frame with substrate water holding capacity (v/v) being a primary promoter of rapid mat coverage. Tray substrate analysis revealed numerous component options provided similar production speeds, with diverse and beneficial physical properties being described. Zebra and Quagga mussel shells proved to be a sustainable and beneficial component option for both mat and tray substrates. Further substrate component identification resulted in Biochar being investigated for its potential use in green roof media mixtures. The additions of incremental amounts of biochar into control substrates reduced bulk density by up to 20%, while simultaneously increasing volumetric water holding capacity to 54%, 12% greater than that of the control. Sedum plant growth in biochar revealed the lowest shoot dry weights resulting from no biochar additions. Substrate and plant water relationships were explored further with four substrates being planted with four diverse herbaceous and succulent plant communities. Substrate composition and plant community was observed to significantly affect dry down rates.