Last spring, California experienced its first super bloom in more than ten years. People flocked from the cities to see this magical display of wildflowers erupt throughout the desert, turning the arid landscape into a sea of brightly colored flowers.

Next decade, you might not have to venture too far from the city to experience the super bloom. Lieve Dierckx, a visiting scholar from ZHAW and short-term resident at swissnex San Francisco, is researching the best way to build and maintain a garden bed on a San Francisco residential rooftop, using only native wildflowers that do not require watering.  

It’s a timely project. The world is experiencing rapid urbanization: the United Nations Development Program predicts that by 2050, 66% of the population will live in cities, up from 54% today. This dramatic migration into our cities in such a short time frame will place a huge strain on resources and energy requirements, forcing residents and governments to implement sustainable living solutions.

 

REIMAGINING SAN FRANCISCO’S ROOFTOPS

Lieve’s project aims to bring nature into cities. By reimagining San Francisco’s residential rooftops, Lieve has found a new home for native wildflowers to flourish. Currently, native wildflowers can be found scattered around the city: beside roads, on vacant blocks, and other wasteland areas. Many native wildflowers have adapted to grow in harsh conditions of drought-affected, sandy soil and do not require watering. That means they’re perfect for San Francisco’s residential roofs, which have a low load capacity and are unable to support the weight of plants that require a large volume of soil or water. By modeling and varying the substrate depth and adding natural elements, such as wood and rocks, Lieve has created a variety of microclimates in her rooftop gardens. This provides varying conditions for the plants to thrive in, and offers a wider range of habitats for local fauna.

Lieve is no stranger to San Francisco, and knows which of the city’s roof tops have the best views of the city. In 2015, Lieve created a small 4 plot (1.2m squared) rooftop garden seeded only with native plants at the Drew School as part of a research project and residency with swissnex San Francisco. She has returned to the city twice to expand and develop this project into a larger rooftop garden project, with the aim to bring flora and fauna into the city – and to influence city planners, who are turning to greener initiatives to meet the demands of the future. Lieve has chosen plants that are not only pleasurable for the eye, but have a high ecological value, offering habitat for fauna (such as pollinators).

 

THE BENEFITS OF GREEN ROOFS 

Research shows that there are many benefits of green roofs to a city, including lessening energy demands; reducing heating and cooling requirements; reducing stormwater runoff and resulting pollution; capturing gaseous and particulate pollutants; alleviating urban heat-island effects (cities of concrete and tarmac retain heat and create urban heat islands that are much hotter than surrounding suburbs – plants through transpiration directly cool the air and can reduce surface roof temperatures dramatically in summer); improving sound insulation; promoting longer roof lifespan, and increasing biodiversity. Research also suggests that if all roofs in a major city were green, urban temperatures could be reduced by as much as 13°F.

San Francisco is home to many plant communities that do not require watering and thrive in poor quality soil, or little soil at all. These are the types of flowers that Lieve has sourced for her extensive natural living roof concept and include California poppies (Eschscholzia californica) and Beach Strawberry (fragaria chiloensis) from the coastal strand plant community, and Farewell-to-Spring (Clarkia amoena) and tidy-tips (Layia platyglossa) from the Valley Grassland plant community.

 

SWISSNEX SAN FRANCISCO’S SUSTAINABILITY INITIATIVES THIS FALL

This project is part of a series of activities at swissnex San Francisco this Fall that explore sustainability and our future. Currently showing at the swissnex Gallery is Climate Garden 2085: a public science experiment imagining future climate effects on San Francisco’s forests, agriculture, and landscapes. The exhibition runs until November 22.


Photo: Native wildflowers growing amongst trash on a San Francisco sidewalk, by Lieve Dierckx.

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