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Editor’s note: This is the first in a series of three case studies on urban ecology. The stories behind photos two and three will be featured in future issues. Three urban locations in San Francisco needed fresh ideas to revitalize their landscapes while addressing problem areas. I was called upon to review these needs and to provide sustainable, “Bay-friendly” landscape management guidance to each building’s property manager and landscape contractors.
Other than the two east and west edges of the courtyard, most of the landscape receives only intermittent direct and indirect sunlight through gaps in the tree canopy, along with reflected light from the building’s ample windows. The imported soil – dense clay, low in organic matter and trending toward alkaline – was challenging as well, as it required close and active management. We began soil testing in 2006, taking samples each spring and fall to guide the soil management program. In addition, the original spray irrigation system was converted to a drip system in order to protect the trees’ health and reduce overspray.  When I was called into the project, the deer tongue fern – native to coastal California forests – was not thriving, and alternative plantings were needed that would maintain the original landscape design. Native rushes and ferns, and two non-native plants, were introduced to provide more biodiversity and to enhance the design and function of the landscape.The catwalk in the lower courtyard created a deep shade condition directly beneath it, and Clivia, a member of the amaryllis family, was selected. It provides the added bonus of providing nectar for pollinators and, en masse, creates a feeling of a meandering waterway. Bordering the Clivia, native chain ferns were planted. Their hardiness and ultimate size filled in a large area where the deer tongue ferns weren’t thriving. They are normally found along creeks and seeps in Northern California. To represent a woodland plant community, hardy western sword ferns were installed, many along pathways where the deer tongue ferns proved too delicate. On a sloped area that was eroding, jute netting and Berkeley Sedge, a hardy, but non-native carex, were installed to stabilize the slope and add texture to the area. Finally, in two low, rock-bordered edges of each courtyard that have poor drainage and streetscape exposure, we planted native rushes, a durable plant that grows along seeps and streams. The native deer tongue fern was replenished in several areas, and its culture improved by misting its leaves in the non-rainy season and by adding organic matter.
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The first property consists of two interconnected, four-story buildings having upper and lower courtyard planters with 97 Himalayan birch trees and ground cover surrounded by 33 Ginkgo street trees. The prior structure was a recycled glass factory, and a glass wall enclosed with industrial steel framing creates a walkway simulating a riverbed. Prior to the city’s construction, the landscape was sand dunes spotted with creeks, marshes and a rich diversity of flora. This information served as valuable inspiration for which plants might be well adapted to the climate and, perhaps, reflect the original landscape design.
The interior courtyard planters had several problem areas requiring solutions that both fit the riparian theme and also succeed in a roof top garden with limited root space.
Explore the January 2011 Issue
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