23 Aug 2014
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Up on the Roof: Gardens Grow to New Heights

Is Getting High the Future of Green Space?

Here’s an extreme makeover ideally suited to sunny California: transform your under-utilized rooftop into a lush garden. Elsewhere in the country, the roof  is fast becoming a mainstay of sustainable, cutting edge design.
This urban solution takes root in two ways. The “green roof” project takes on a grand scale, requiring architectural plans implemented by committee--cities, corporations, developers.

The more individualistic “rooftop garden,” by contrast, celebrates do it yourself ingenuity displayed by homeowners with a yen for getting high.
Both approaches pay big benefits in the form of additional greenery that purifies the air through plants’ release of oxygen. A rooftop plot also captures rainwater and looks far more appealing than pedestrian tar and slate.

Up on the roof, homeowners, renters and condo dwellers can expand square footage with an additional space to grow flowers and raise vegetables. 

And for public spaces, citizens take advantage of the inviting greenery to stroll and commune with nature.


Roof top gardens do call for imagination and tenacity.

Consider the roofprint of your humble Studio City abode. The slope, solar panels, chimneys, vents, satellite dishes, air conditioning ducts all complicate the transition to a green aerie.

Addressing a symposium here last spring, ecologist Paul Kephart cautioned landscape designers to proceed with caution. “Often the rooftops here will have temperatures as high as 175 degrees, so how do we mitigate for that, how do we look for natural analogs. Where in nature do these kinds of plants and soils occur? And how can we learn from nature to look at adaptation and function?"

Kephart, founder of Rana Creek Studio in Monterey, Calif. and a leader in the emerging green roof architecture added, “In heavily urbanized areas like L.A,  [Plants] are exposed to radiation and extreme temperatures.”


Public rooftop gardens in Southern California include Hermosa Beach’s Union Cattle Co., the Standard Downtown, and the Peninsula hotel in Beverly Hill, which features a "living wall" made of palm trees, jasmine and wisteria.

But what about adding a rooftop garden at home? 

Understanding weight loads and the structural integrity of the building is essential before you get started. 

The water-proof membrane is all-important. Vegetated roof systems can easily be adapted to metal standing seam roofs and there are available mat systems that adapt to slope roofs.

Before installing raised beds, lay a protective drainage layer between the soil and the membrane. Topsoil weighs a lot so go easy on the dirt. Experts recommend a ratio of 1/3 clean topsoil, 1/3 compost, 1/3 perlite or other inorganic material.

A decorative rooftop garden provides fewer energy benefits than a “green roof” consisting entirely of vegetation over a larger field.

But any rooftop greenery will cool off a house by reducing the urban heat that is absorbed in the Valley during the summer. Add a trellis and you can grow your own herbs and veggies.

The sky’s the limit when picking plants. Low-water succulents, flowers and grasses thrive up high. Prime candidates include drought-tolerant Lewisia cotyledon 'Sunset Strain' with evergreen foliage; Nassella tenuissima grass with wispy green-to-blond blades to  silver Lavandula multifida Felty, a Mediterranean shrub topped with violet blooms.

Other rooftop heroes: most every groundcover Sedum from Cape Blanco’s tiny blue-green rosettes on trailing stems to Voodoo's small, rounded burgundy leaves;Libertia peregrinans with stiff orangey blades reaching 2 feet tall; inky purple aeonium. Delosperma “Lavender Ice.”

Rooftop gardeners also gravitate toward Allium schoenoprasum, agapanthus, lavender, lemons, kumquats, tangerines and olive trees. And Sedum and other shallow-rooted plants that tolerate the hot, dry, windy conditions.


The large scale green roof movement has produced spectacular urban transformations. 

Manhattan’s High Line, built in the 1930s as part of a massive public-private infrastructure project 30 feet in the air then abandoned in 1980, was reborn as a public park. Its invention was the result of the ingenious and intrepid: Friends of the High Line, the City of New York, landscape architects James Corner Field Operations, architects Diller Scofidio + Renfro. It is now the biggest tourist attraction in the city.

In Chicago, Mayor Richard Daley built a garden on the roof of City Hall 7 seven years ago. Laughed at by many and considered a big waste of money at first, it is now a prototype being considered by the City of Los Angeles. The garden helped the building become more energy-efficient by retaining rainfall in the soil and cooling the building from the top down. The Chicago garden roof will last twice as long as a traditional roof and has provided the city with praise-worthy scenery More than 200 other buildings in Chicago are now topped with gardens.

San Francisco’s California Academy of Sciences utilized innovative and sustainable strategy for those tricky sloped roofs in a design by Renzo Piano. Porous, biodegradable interlocking trays were fabricated for plants and were installed onto the roof like tiles. Also erected was a wide grid of wire mesh cages filled with rocks, which provide additional support. 1.7 million native plants insulate the roof, capture rainwater, and provide a 2.5-acre habitat for butterflies and birds.

Locally, UCLA ‘s Court of Sciences Student Center's rooftop garden champions the case for green construction in Southern California.


Install an herb garden of thyme, oregano and chives or pockets of pocket of gardenias, and kumquats to camouflage ducts or pipes.

Collect rain in a barrel or run a garden hose up the side of building. Attach it to drip lines and a timer system.

Reduce the need for weighty soil by using interlocking plastic cells, which can be found as a staple of hydroponic systems.

To reduce weight, use lightweight fiberglass planters; fill pots with a mix of soil and foam packing peanuts.

For more ideas, attend the California Landscape Contractors Association (CLCA) Industry Show February 1-2 in Los Angeles.


Turn your entire roof into a trellis.

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