Turf is not an obvious choice for a green roof plant because it requires so much maintenance. It's an especially adventurous bet for an irregular surface like the new green roof at New York City's Lincoln Center for the Performing Arts, a roof that one design blogger has likened to a "Pringle." Even on flat ground, a lawn is hardly ever a low-maintenance landscape. On a roof, it needs an extra-deep layer of growing medium-at least eight inches deep to give proper horticultural support to its root system. A simple sedum roof requires only about four inches. The greater depth needed to grow turf, in turn, requires a higher structural capacity to hold up the roof, which adds considerable cost to a project. At Lincoln Center, owing to the compound curves that shape the roof like a saddle, the planting depth ranges between eight and 12 inches.
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