The Guardsman

24 October 2008 Science 117 views No Comment Print This Post  Email This Post

Though the rooftop gardens atop the Orfalea Family Center on Ocean Campus lack flowers and are turning brown, these hearty perennials are simply entering a normal annual phase. ANNABELLE DAY / GUARDSMAN

By Roxanne Bequio
Staff Writer

The plants growing on the Ocean campus’ Orfalea Family Center roof not only distinguish it from all the other buildings, but also serve as an environmentally friendly, sustainable, and self-sufficient alternative to other rooftops said Demetri Gonzalez, City College’s senior project manager.

A living roof system is made up of planting trays which are often biodegradable, a soil or gravel medium for the plant’s roots to grow in and take hold of, the plants themselves and a supplemental irrigation system, primarily used to get new plants established, said Gonzalez in an email.

Living roofs also provide the benefit of natural water filtration, said Gonzalez. “With a living roof, rain water is filtered by the plants and since no fertilizers are used, only clean water is returned to the Earth.”

The specific difference between living and traditional rooftops is in the top layer or the visible part of the roof, which is exposed to the elements. This part of the roof is made up of living plants instead of man-made materials, such as rubber, tar, asphalt, or steel.

Students walking past the Orfalea Family Center on Judson Avenue can get a closer look at the living rooftops from the sidewalk. At first glance the plants, a species called Sedum spathulifolium, seem to be withered and dying, but are indeed alive.

“They are simply entering a phase of their annual cycle where the flowers die off, and they turn a burnt umber color. This is completely natural for the species of plant being used. Sedum plants are one of the most rugged, durable perennials available, and are often described as ‘tough as nails’. The chosen plant doesn’t require much watering and can survive simply on the amount of annual rainfall we get here in the Bay Area,” Gonzalez said.

According to the plants database for the United States Department of Agriculture’s Natural Resources Conservation Service, Sedum spathulifolium is native to the northwest region of North America, and can be found along the coast from British Columbia down to California.

From spring to summer this low growing plant blooms and forms clusters of yellow star-shaped flowers. The leaves are shaped like rosettes, and appear silvery green in color until autumn, when they become bronze, red, or umber. The Sedum’s flowers fall off on their own and help the spreading of more seeds and the growing of new, additional plants.

Sedum is easy to grow, and capable of growing in dry soil during drought due to its thick, fleshy, water-storing leaves, said Gonzalez.

Although the sedum are basically left to grow naturally and unaided due to their self-sufficiency, the roof still gets examined regularly as a precaution for the livelihood of the plants and the rooftop itself. “The cost to maintain such as system is nil,” Gonzalez said.

“A living roof helps achieve ‘sustainability’ by keeping the building interior at a more constant temperature, thereby requiring less mechanically provided heating and cooling,” said Gonzalez.

The rooftops were put in by Elevated Landscape Technologies Inc., a green roofing company from the province of Ontario in Canada. “Since its initial installation over a year ago, [Elevated Landscape Technologies Inc.] has performed routine visits of the site and confirmed that all is well,” said Gonzalez.

City College student Christina Martinez, 25, believes with the living roof the college took a step in the right direction. “I feel that it’s a closer step to perhaps being sustainable, and a good example for the rest of the community. I think it’s a good thing,” Martinez said. “I haven’t noticed any other buildings that are like this around San Francisco, or where I live in Daly City.”

“Currently, there are no issues with the living roof at the Child Development Center. The roof doesn’t leak and the plants are growing as expected,” said Gonzalez.