As forests, agricultural fields, and suburban and urban lands are replaced with
impervious surfaces resulting from development, the necessity to recover green space is
becoming increasingly critical to maintain environmental quality. Vegetated or green
roofs are one potential remedy for this problem. Establishing plant material on rooftops
provides numerous ecological and economic benefits, including stormwater management,
energy conservation, mitigation of the urban heat island effect, and increased
longevity of roofing membranes, as well as providing a more aesthetically pleasing
environment in which to work and live. Furthermore, the construction and maintenance
of green roofs provide business opportunities for nurseries, landscape contractors,
irrigation specialists, and other green industry members while addressing the issues of
environmental stewardship. This paper is a review of current knowledge regarding the
benefits of green roofs, plant selection and culture, and barriers to their acceptance in the
United States. Because of building weight restrictions and costs, shallow-substrate
extensive roofs are much more common than deeper intensive roofs. Therefore, the
focus of this review is primarily on extensive green roofs.