Can a green roof catch fire and spread fire?

Not if the green roof is designed correctly. In Germany, green roofs actually have a better fire rating than conventional roofs because the mineral media layers cannot burn. The extensive use of sedums (a type of succulent) in Europe, the northern United States and southern Canada, as well as gravel borders and breaks also protect against fire. In our arid, fire-prone Southern California region, we engineer the system with fire-retardant features, paying special attention to mineral content, gravel layers, and plant selection.