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Environment | Communities

Seattlites Learn What Will Grow in the Nation's First Rooftop Community Garden

SEATTLE —- Scott Mills visits a parking garage on Mercer Street in Seattle every day to tend to his garden.

If the top of a parking garage sounds like an unusual spot for a 30,000 square-foot community garden, it is.

“This is the first rooftop community garden in the country,” Mills says, as he shows off his rutabagas and plucks the flowers off the purple basil plants.

It’s called UpGarden and it’s part of an effort to increase the amount of community gardens in Seattle’s densely populated Uptown neighborhood, where there was limited on-the-ground green space available to build such a garden.

Nancy Coe knows firsthand just how limited. She lives nearby in the Belltown neighborhood and had been on a waitlist for community garden plot for 5 years before she heard about plans to build a garden on the underutilized top floor of the Mercer Parking Garage, which was originally built to accommodate motorists visiting the 1962 Seattle World’s Fair.

Coe attended the first meeting last December and thought, “Holy moly this is cool! But how are we ever going to pull this off?”

It wouldn’t be easy. They had about $150,000 to work from the 2008 Parks and Green Space Levy, which comes to about $5 per square foot.

Landscape architects Eric Higbee and Nicole Kistler with the firm Kistler Higbee Cahoot were hired to work with community members to design the project.

“It was very challenging,” Higbee says. “We were dealing with a 50-year-old parking structure and it turns out cars aren’t that heavy compared to saturated soil.”

20120829kc-up-garden-6 Parking garage’s sloping surface

Soggy soil can easily weigh more than 100 pounds per square foot, but the garage was built to withstand more like 40 pounds per square foot. Higbee consulted with urban gardening experts to find lightweight soil mixtures and wood chips, which were pumped four floors up.

The second challenge was to build a garden on the sloping surface of the parking garage without all the soil sliding off in the rain. Higbee says that they decided to build terraced planting beds of wooden boxes, which are lined with a fabric that allows water to pass through, but not soil. The boxes were filled with about 12-18 inches of soil, which is adequate for more vegetables and flowers. Earlier this spring, the 100 or so plots were divvied out and gardeners began planting in May, Coe says.

Over the past few months, gardeners have been trying to figure out what plants can withstand this unique micro climate. Already they’ve learned that plants in UpGarden are prone to drying out under the direct sun and windy conditions, so volunteers have installed a slow-drip irrigation system.

Each gardeners is experimenting with various plants, Mills says. Pointing out a pair of sad-looking begonias, Mills says that shade-loving plants aren’t going to last long here.

“But cherry tomatoes,” Mills says. “We’ve had a lot of luck with them.”

Gardeners have also had success with tomatillos, sunflowers, herbs, and even sweet corn. They also grow enough lettuce to have regular Sunday salad feasts on the rooftop.

Higbee says UpGarden has exceeded his expectations.

“It’s finally gotten green,” Higbee says, “and to see this lush green roof top among all this concrete is really spectacular.”