STUDY TO EXPAND THE RANGE OF WILD PLANTS FOR EXTENSIVE ROOF GREENING SYSTEMS USING SUPERABSORBENT POLYMERS (SAP)

Members of Sedum family and mosses are heavily used for existing extensive greening systems providing a thin vegetation layer with low water capacity. This leads to a monotonous visual appearance of the vegetation. The aim of the present study was to evaluate a range of wild plants for extensive roof greening systems under the environmental conditions of Berlin by using superabsorbent polymers (SAP) in different concentrations. The substrates used were expanded slate crushed 1/11 mm + 1 g SAP/L substrate, expanded slate crushed 1/11 mm + 3 g SAP/L substrate, expanded slate crushed 1/11 mm + 10% organic matter, and expanded slate crushed 1/11 mm as a control. The species tested were, Anthemis carpatica, Armeria maritima, Cerastium tomentosum, Dianthus carthusianorum, Dianthus deltoides, Euphorbia myrsinites, Gypsophila repens, Leucanthemum vulgare, Linum perenne, Saponaria ocymoides, Scabiosa lucida, Veronica spicata‚ ‘Nana’ and the experiment commenced in May 2004. The substrates with 3g L^-1 SAP gave the best results in view of the degree of coverage and regeneration under the climatic conditions of the years 2005 and 2006 which had long dry periods. The plants growing in substrates with SAP were healthy and vigorous and showed fewer negative effects from the dry periods. Water supply was enhanced with SAP so that a wider range of perennial species can be used in this system under the environmental conditions of Berlin, including Cerastium tomentosum, Dianthus deltoides, Gypsophila repens, Saponaria ocymoides, Dianthus carthusianorum and Euphorbia myrsinites.