The Sedum species is a common choice of plant for commercial extensive green roofs. F. rubra and A. stolonifera are both common British grasses, which can grow on turf roofs, and P. lanceolata is a common invasive species on green roofs ( Dunnett et al., 2008). Trays of the four species were grown from seed, or washed cuttings (S. album), in a ‘magnetically clean’ greenhouse at the control site. John Innes number 3 compost was used. Trays of mature plants were then placed on the two study roofs on 03/07/2011. Additional trays were left in the greenhouse at the control site. Trays containing just compost were also placed on Roof 2 and in the control greenhouse to investigate soil metal concentration changes when plants are absent. In dry periods, plant trays were watered with pre-collected rainwater direct to the soil layer to avoid artificial rain effects of washing particles from the leaf surfaces.