Native plant species top California's living roof

This summer, contractors installed the largest living roof in California -- a 2 1/2-acre expanse at the new California Academy of Sciences building in Golden Gate.

The roof features seven hills blanketed with nine native plant species.

Plants include four perennials (Fragaria chiloensis, Armeria maritima, Prunella vulgaris and Sedum spathulifolium) and five annuals (Eschscholzia californica, Lupinus bicolor, Lasthenia californica, Plantago erecta and Layia platyglossa). Rana Creek Nursery in Carmel, Calif., grew the 1.7 million plants used for the installation.

“Our goal was to choose native plants that were well-adapted to the climate in Golden Gate Park and would provide much-needed habitat for native birds, butterflies and other beneficial insects,” said botanist Frank Almeda. “We also needed to select species that would look attractive throughout the year, since a visually appealing roof is a much more powerful educational tool.”

The nursery created porous biodegradable trays using tree sap and coconut husk fiber to contain the plants.

The trays were installed on the roof like tiles. The segments will lock together as the plants’ roots grow and penetrate adjoining trays.

The roof, padded with 6 inches of soil, will provide excellent insulation, keeping interior temperatures about 10°F cooler than a standard roof. It also will decrease the urban heat island effect, staying about 40°F lower than a standard roof. The roof will absorb about 98 percent of all storm water.

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For more: California Academy of Sciences, (415) 321-8000; www.calacademy.org.