Winter rains have helped prepare Golden Gate Park’s newest and most native habitat to flourish this spring.
The carefully managed experimental ecosystem that occupies the undulating 197,000-square-foot rooftop of the California Academy of Sciences has evolved in the 17 months since the new building opened.
The living rooftop slopes up and down to form large mounds that create microclimates, with some areas windier and drier than others, which has helped to create a tapestry of native plant populations.
“In time, some species are going to thrive in certain habitats while others won’t do as well,” academy botanist Frank Almeda said.
Academy officials grew the roof’s first nine species of native plant seedlings in 50,000 trays that were made out of coconut husks and placed directly on the rooftop.
Since then, dozens of additional native plant species have been introduced and others have established their own rooftop populations, according to Almeda.
Trees and other woody species that spring up on the roof are yanked out by gardeners.
Willow trees that started growing are believed to have come from a population near the Carmel Valley nursery where the coconut trays were filled with dirt and seeds.
Pine saplings and other woody species spread naturally onto the roof, presumably by taking advantage of the seed-spreading functions of birds, according to Almeda.
The increasingly diverse rooftop is as sparse as most local wintertime habitats, but its spring blossoming is expected to be its best yet.
“With all the rain we’ve been getting, spring will be quite interesting,” Almeda said.
The plants have provided a new home for insects inside Golden Gate Park, which was built on former sand dunes.
San Francisco State University graduate student Jessica Van Den Berg recorded 70 species of predacious beetles, parasitic wasps and other insects living on the roof during two years of studies.
Pygmy grasshopper species that hitched a ride to the roof from Carmel Valley have been surviving better than would be expected in San Francisco’s comparatively dry environment, Van Den Berg said.
“I guess the fog drip has helped them to stay here, but I would think eventually that it’s going to dry out too much,” she said.
Dominant native species planted on academy roof
- Sea pink
- Beach strawberry
- Self heal
- California poppy
- California goldfields
- Coastal tidy tips
- Sky lupine
- California plantain
Source: California Academy of Sciences