The vertical garden at the Drew School in San Francisco is the first major living plant wall in North America designed by world-renowned French botanist Patrick Blanc. On the east facade of the school’s performing arts building, 5,000 plants of 150 different species grow from a special felt mounted on a stainless steel lattice. It’s a surreal sight, enough to stir the imagination of any passerby on Broderick Street.
Installed in February 2011, the project was a collaboration between Blanc, SF-based Roma Design Group, and Rana Creek, an ecological design firm based in Monterrey. Blanc designed the plant layout. Roma designed the architecture. Rana Creek provided and installed the plants.
The stainless steel lattice is offset eight inches from the actual building. It supports PVC panels onto which are stapled two layers of Blanc’s proprietary polyamide felt. Pockets are cut into the outer felt layer to support the plant roots. Tubes, called emitters, deliver water and a liquid fertilizer to the plants. The water seeps down through the felt and plant roots until about 10 percent runs off into drains at the bottom. In some of Blanc’s designs, the runoff is re-circulated into the system, but due to financial and spatial constraints, this is not the case at the Drew School.
The vertical garden is essentially a hydroponic system. It is irrigated three times per day, seven days a week. On average, it uses 250 gallons per day. The liquid fertilizer is a highly concentrated and broad mix of nutrients. During the first few months after installation, the mix recipe was continually tested and tweaked to fit the needs of the California native species. Just before Blanc visited the garden in October of 2011, a correct recipe was achieved and the plants suddenly began to flourish. Needless to say, Blanc was very pleased.
The building also has a living roof composed of entirely California native species. Installed in lava rock gravel, 1,252 18-inch coconut-fiber biotrays filled with soil cover the entire roof. A subsurface irrigation system waters the roof once a day, seven days a week.
A scientist from Zurich, Germany has set beetle traps for a study of beetle populations on living roofs. Another scientist installed artificial habitats for a study of solitary pollinators such as bumblebees. The garden attracts hummingbirds, butterflies, and of course student enrollment has increased.
A wall of solid foliage tends to encourage fantasy. Perhaps I’m not the only one who wonders what if every building in San Francisco had a vertical garden…