Monterey County Magazine - Summer, 2008
Living Roofs connect Nature to Architecture
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High up on a blustery Big Sur ridge, silvered native bunch grasses and golden poppies ripple in the wind, lit by the sun glancing off the white-capped Pacific. Thousands of miles away, busy office workers gaze out of downtown Chicago skyscrapers at a massive stained glass dome that appears to grow out of a Midwestern meadow of prairie coneflowers, fragrant thyme, and rosy flowered sedums. What do these two very different scenes have in common? They are both living roofs.
Here in Monterey County, the idea of the living roof is often one of aesthetics. Dramatic modern homes are built into the coastline then hidden beneath a mantle of soil and native plants to help maintain ocean vistas and scenic views. But beyond the beauty, living roofs are a way to connect architecture directly to the landscape and provide valuable assets to our gardens and environment.
The term living roof is a broad one, but mostly concerns rooftops where layers of specialized roofing and drainage material are topped with several inches of soil and then planted just like a garden or meadow. Plant selection is crucial because the roof is an unforgiving environment. It is exposed to the elements, from blazing sun to bitter cold, snow, and wind. The shallow soil base means it will dry out faster than the surrounding landscape. Plants chosen for the roof should be low growing, drought tolerant and cold hardy, like the many types of sedum and hardy iceplant, Delospermum.
Most importantly they should have the ability to self-replicate. The harsh environment of the roof means that some plants will die from time to time and if their neighbors can send over a runner to root or drop of few seeds to fill the gap, all the better.
The roof can also be a haven for wildlife and beneficial insects. In Chicago, the city’s Cultural Museum hosts a colony of honey bees that gather nectar from thyme blooming on the roof and flowers in the traffic islands that make the Magnificent Mile look so magnificent. City employees, who take real pride in the productivity of hives placed at the museum, city hall, and various schools and firehouses across the Gold Coast area, tend the hives. Migrating birds roost on the rooftops, scratching for seeds and insects among the thick tapestry of plants.
In Big Sur, the living roof acts like a habitat surrogate. Where grazing and construction damaged native grasslands, the new living roof is an opportunity for delicate wildflowers to find a home. The land beneath the home has literally been reborn up in the air, resulting in new places for rare Smith’s Blue butterflies to seek a mate or suck on the nectar of the pink buckwheat or deep blue larkspur.
The living roof is, most importantly, a living sponge for rainwater. As more of the landscape is covered with paving and rooftops, rainwater is shunted into storm drains and sewers, never having a chance to soak into the soil. The thick mat of roots and soil on the roof is the first to catch the winter rains. The roof slows the runoff, taking what it needs, and depositing the rest slowly for us to use. This lessens the impact of rain events on public sewers and reduces the likelihood of flooding. And in conjunction with rainwater harvest tanks can provide a source of clean water for irrigation and fire protection come summer.
Now the plant palette for the roof is amazingly diverse, although I have even seen vegetables grown 20 floors in the air, California native and dune plants are particularly well suited for this assignment. Many natives, such as the beach strawberry, Fragaria chiloensis, with glossy dark green leathery leaves and tiny white flowers, spread slowly by runners. Achillea millefolium, the common yarrow, is another. Soft, ferny, aromatic foliage is topped with flat flower clusters in white or pink that is a favorite of passing butterflies. Thymus vulgaris and Thymus citrodorus are perfectly suited to the rooftop as well. With fragrant foliage and lavender flower spikes only a few inches tall, they can withstand both foot traffic and bitter cold. The Sulfur Buckwheat, Erigonum umbellatum, offers sulphur yellow bloom clusters over silver crinkled foliage that grows naturally from deserts to high mountains.
The living roof as a continuation of the ground level landscape is an aesthetically pleasing system. Not only does it provide rainwater harvesting, it also gives birds, insects and plants a habitat in an increasingly fragmented wild landscape. The living roof can further connect your home with the natural world, making the neighborhood that is Monterey County a better place for people, plants, and wildlife.
