The Issue of Green Roofs

By: Lorene Edwards Forkner, editor Lisa Lee Benjamin
Lisaleebenjamin

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http://www.lisaleebenjamin.com

Lisa Lee Benjamin perseveres in her worldwide pursuit to generate environments that unite people, art, and science. Consulting and collaborating…

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At Pacific Horticulture we try and dig deep. The best part of my work is pulling together a mix of stories around a particular theme that explores the world from a horticultural perspective.

In recent months I’ve been working with Lisa Lee Benjamin to take a fresh look at green roofs. As my guest co-editor, Lisa invited friends, colleagues, and plantspeople, to write about developing views, creating habitat, low-tech innovation, and—perhaps most importantly—plants appropriate to West Coast growing conditions. It’s been an exciting and productive collaboration. I’ll let Lisa introduce the topic:

Spring wildflowers on the California Academy of Sciences roof. Photo: Lisa Lee Benjamin

Spring wildflowers on the California Academy of Sciences roof. Photo: Lisa Lee Benjamin

Imagine an endless sea of sky gardens, from Canada to Mexico, providing seasonal beauty, critical wildlife habitat, stormwater management, life-saving heat island reduction, energy savings, and, as you will read, even rare plant conservation. A lovely picture isn’t it? Yet lack of knowledge and fear of liability leads to complex engineering and overdesign, unhealthy marketplace competition, proprietary products, and  expensive green roofs that benefit only a handful. At the moment, this green sea of possibility exists only as a few tiny islands.

Green roofs require critical thinking and a mix of horticulture, design, engineering, and  science. Yet any garden—whether it is on the ground, on top of a garage, or 15 stories up—is subject to natural law and will work if a few basic principles are taken into account. It can be very simple if we

use  the most advanced technological instruments we have:  our brain  and observation. What do we see?  Water flows downhill; geology and soil/ substrate composition determine plant communities, drainage, and fertility; legumes produce nitrogen; plants provide food for insects which provide food for birds, and  so on.

Useful patterns and tools begin  to emerge when  we observe our surrounding landscapes, whether it’s the golden coastal hills with their  spectacular show of annual ephemerals, resilient vacant lot plant communities, or persistent dandelions in our cracked sidewalks. Valuable knowledge and insights on how to design successful green roofs that add tremendous value to our urban ecosystems are all around us. We just need to pay attention.