These are the sedum mats for the Water Department's "islands" exhibit. They're an example of both creative design and reinvention. The reinvention part involves Ed Snodgrass, a fifth generation farmer in northern Maryland who realized in the late 1990s that he was not going to be able to make it as a dairy farmer.
The thought of a family farm of 150 years' duration going under on his watch was too much. So Ed did some soul-searching and research, and decided to stake his claim to the green roof market, which wasn't nearly the big deal in this country that it is now. It was a pretty brave choice, but Ed's Emory Knoll Farms is well-established in the field now.
On my trip to visit him several years ago, I was struck by the development that surrounds his property, fellow farmers who did go under or couldn't resist the offers from developers. I was struck by two other things - the tremendous versaitility of the sedums and other succulents he was growing; they're really beautiful, in addition to be workhorses for good drainage and low maintenance.
The other thing that's interesting is this: You can do a "green roof" almost anywhere. It doesn't have to be a roof per se. The Water Department exhibit uses Ed's mats to show that monoculture lawns can be replaced with useful, attractive and environmentally smart alternatives.