why stop at green rooftops?

After looking into green roof techniques, I came across green walls and, specifically, the vertical garden techniques created by Patrick Blanc. I’m not entirely convinced on how or why it works, but I’m sure he’s trying to keep as much of it a secret as possible, otherwise he’d be out of a job. What I do know is that the key to the idea is that the system does not use soil, but rather a cycle of mineral-filled water that is absorbed by the plants as needed. In a technical sense, this system is interesting, but it also allows the opportunity to create very aesthetically pleasing designs, which are much more widely appreciated than the engineering marvel that is vertical gardening.