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Latest Technology in Green Roofs in Golden Gate Park

Written by: Joan Bergsund

When I first moved to California, I lived in San Francisco for several years. On rainy weekends we would spend hours in Golden Gate Park at the DeYoung Museum and the Academy of Sciences/Steinhart Aquarium. Both buildings sustained damage during the Loma Prieta earthquake in 1989 and have been totally rebuilt. The DeYoung reopened several years ago, an architectural configuration still drawing mixed reviews. The Academy of Sciences opened in late September and is enjoying a rush of excitement, curiosity, interest, and praise.

The building, according to their brochure “sets a new standard for sustainable architecture. Supported by recycled steel, insulated by recycled blue jeans, powered in part by solar panels, and topped with a living roof, the building is the epitome of energy efficient design.” I found it amusing and intriguing that recycled denim has been used to insulate the building. Jeans rock!

Of particular interest to me is the green roof which you have read about in this column before and seen pictured in many current publications. I couldn´t stay away, and was among the throng of curious visitors the first weekend. As gardeners, we can be interested in and inspired by gardening practices everywhere.

I took scant time to inspect the many outstanding displays, including the famed albino alligator, and then hastened to the roof, my primary interest. I took the elevator to the third level to gaze upon 2?« acres of living roof planted with native California plants. The seven hills of San Francisco were replicated as the surface undulated over the top of the planetarium and the rain forest. I thought it could also be interpreted as our Tuolumne County rolling foothills.

The docent was well informed and as she spoke I took notes. The engineering to create this roof is staggering. The seven layers of varying materials weigh 2.6 million pounds, including the soil and plants. The 1.7 million plants were selected, planted in 50,000 trays made of coconut husks and installed months before the building was open to the public. When they were installed upon the roof, the trays were tightly packed to assure the plants would not slide or give way to forces of gravity. The trays are biodegradable and will simply mesh with the growing medium in several years. There are rock filled drainage swales to siphon off water once the trays are saturated, and this water is collected in a cistern used for other purposes such as flushing toilets.

Many of the plant species are familiar: sea pink, beach strawberry, self heal, stonecrop, California poppy, California goldfields, tidy tips, sky lupine and California plantain. They look healthy and robust at this initial stage. The contiguous area on the observation terrace is also planted with hundreds of natives, and they too looked well established. The docent handed out lists of the plants, a thoughtful service.

To quote from one of the several brochures, “The museum´s most iconic green building feature, the roof provides superior insulation, prevents storm water runoff, reduces the urban heat island effect and creates a new habitat for native birds, butterflies and other local wildlife.” The Bay checkerspot butterfly, once thought extinct, is again visible due to the creation of its required environment.

When you are next in San Francisco, allow lots of time for a visit to the new Academy of Sciences in Golden Gate Park. Check their website first for additional information: www.calacademy.org

Joan Bergsund, Tuolumne County master gardener, visits Golden Gate Park, the DeYoung Museum and the Academy of Sciences several times a year. Though these buildings are new, the space between them still features the old bandstand with the plane trees which enhance the acoustics when music is being performed.