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The depth of growing media on green roofs can strongly influence plant growth and survival. The setting of the roof, including wind exposure, shading and the nature of the building below the green roof can also impact microclimate and plant performance, but the effects of roof setting have been little investigated. We conducted a five-year experiment in which green roofs differing in substrate depth and the nature of the underlying and surrounding structures (heated/air-conditioned vs. non-air-conditioned space underneath; height of green roof relative to roof surface) were planted with the same mixture of 11 species. After five years with no irrigation or weeding, planted species were still present in all treatments, but communities were dominated by ruderal species that colonized from the surrounding area. Both substrate depth and exposure affected plant community composition with exposure making a larger …