Sharing the rooftop garden secret

The sweet musk of potatoes. The earthy tang of carrots. Red strawberries plump on the vine. The senses delight when a gardener’s labor transforms sun, water, soil, and seed into homegrown produce. What’s growing in Swee and Lisa Sim’s garden could be found in any backyard, but what makes their garden special is that it’s not in their backyard. It’s on their roof.

With the help of volunteers and a bit of inspired experimentation, the Sims, owners of the organic and fair trade retailer Future Green, installed a rooftop garden above their 2352 S. Kinnickinnic Ave. business May 4. The sense was, “Let’s try this and see what happens,” said Lisa Sim, who hopes their project will inspire other business and property owners to consider using their flat roofs for growing space.

The Sims are starting small, planting strawberries, leaks, peas, carrots, and other vegetables in six rooftop growing stations, with a total of 12 planned. Each growing station is a blue 55-gallon barrel sawed in half lengthwise, split apart, and set on a wooden pallet with the two round sides down. They look a little like makeshift rafts or tankers, floating above roughly 1,700 square feet of Future Green’s black rubberized roof. 

On May 4, Swee Sim led a bucket brigade to fill these containers, which in a former life transported fruit juice concentrate, with perhaps a more precious commodity-compost. Volunteers hauled pails of mushroom compost, an eco-alternative to peat, from a five-yard pile spread in the small business’ backyard onto a scaffolding. (Mushroom compost is peat moss and sterile horse manure plus straw and worm castings.) From there, they heaved them up onto the roof to fill the six growing stations that had been placed there earlier. Volunteers from the Urban Ecology Center, the Victory Garden Initiative, and others interested in urban gardening made quick work of the task.

In addition to the space-saving novelty of being up on a roof, these garden units are unique because they are irrigated from below. The growing stations are connected to a water supply by long, thin strands of white PVC pipe that feed into the bottom of each barrel unit. The idea is the same as what makes a soaker hose work-perforations in the PVC pipe allow water under low pressure to seep into reservoirs in the growing stations.

Watering a rooftop garden is a challenge, and conserving water was one rationale for watering from below.

“Your biggest enemies on the roof are going to be wind and evaporation,” said Bruce Rautmann, who helped design the growing stations, which are similar to trademarked EarthBoxes marketed to apartment dwellers and others without yard space for small gardens. (Rautmann is proud to say the materials cost of his units is just $5.25 per barrel, for the PVC pipe, compared to $55 for the trademarked containers, which offer half the space.)

Because of its exposure on the rooftop, compost can dry out quickly, requiring daily or twice-daily watering. But top-down watering with a sprinkling can or hose wastes the water that simply evaporates on the surface without reaching plant roots. So at Future Green, they’re trying a bottom-up strategy.

Rautmann explained that each growing station is watered through wicking stations, perforated plastic bowls packed tight with saturated earth lying at the bottom of each half-barrel. The wicking stations connect the compost above with the reservoir at the bottom of each barrel through cut-outs in a layer of landscape fabric, made of recycled corn, that separates compost above from reservoir below. The fabric is permeable, allowing water but not compost to drain back into the reservoir.

Much like self-watering potted plant systems, the earth above is expected to draw the water up through the wicking stations as it dries. This capillary action should keep plant roots watered but not waterlogged. Rautmann said this design should also allow plants with different water needs to be planted side by side.

As if that simple but innovative design weren’t green enough, solar panels on Future Green’s roof will power the water pump, formerly used to pump biodiesel, that irrigates all the rooftop garden units simultaneously through the PVC pipe network. The solar-powered pump draws water from two 200-gallon tanks that collect rain from the roof and can also be connected to the municipal water supply when more water is needed. More growing stations can be added later just by adding more piping.

Seeds of Change

Future Green’s rooftop garden is part of a larger pattern of Milwaukeeans thinking and acting about local food.

“The most important thing to realize is we need to localize our food supply,” said Gretchen Mead, head of the Milwaukee chapter of the Victory Garden Initiative, which promotes urban gardening wherever possible. Ever the advocate, Mead helped move compost at Future Green May 4 while her 7-month-old son Otto, in his blue PJs, was strapped to her chest in a sling.

“We’re not always going to have access to cheap, abundant fossil fuels” to transport food across the country, she said, launching into a constellation of criticisms of food that comes “1,500-miles-per-bite,” maligning the nutritional defects of “food on steroids,” and criticizing the industrial agricultural practices that she said contribute to disease mutations, the need for antibiotics, and global health crises like the swine flu epidemic.

Mead sees local gardens, if not as a panacea to these ills, then certainly as the most reasonable way forward. She argues that building local food supplies not only connects people to their food and encourages healthier lifestyles, but also connects people to each other-building stronger communities.

Bay View resident Tom Brandstetter, who hauled compost May 4, provides one example of how such communities are starting to take root.

A Future Green customer, Brandstetter is also part of the Transition movement, which seeks to create community opportunities by breaking our fossil fuel addiction, building a post-oil economy in the face of peak oil and climate change.

“A lot of this information out there is so depressing, it’s just good to get your hands dirty and do something,” said Brandstetter.

He sees rooftop gardening as a model that could be exported not just to Western cities, but to the Third World, especially in lower latitudes, where he believes rooftops could restore space for food production lost to rapid urbanization.

Inspiration

The Future Green building was designed to bear the load of a green roof, and the Sims initially looked into installing a living roof that would improve their insulation and better manage stormwater. But Lisa Sim said two companies estimated the cost of installing such a green roof at $20,000 to $30,000, which scared them off this tack. Then last year, they watched a film about peak oil with friends and started thinking about community gardens and action on a smaller scale.

The Sims were inspired by Erik Lindberg, who last year built and planted 16 raised garden beds on the 5,000-square-foot roof of his Milwaukee business, Community Building and Restoration.

“Roofs are really tremendous wasted space,” said Lindberg, who this year has started a 10-share CSA farm from his roof. (CSA is for Community Supported Agriculture, where subscribers buy shares in a local farm and receive fresh produce as dividends.)

Lindberg sold seven shares so far, for what he said may be the first rooftop CSA in the nation. With the aid of makeshift greenhouse “hoop houses” over his beds, this year he’s already harvested lettuce planted in February. His original goal wasn’t to make a garden-he wanted to make his business below a net-energy producer by adding solar panels. These proved cost-prohibitive, but Lindberg said it led him to look at his underutilized roof as an opportunity instead of a liability.

After meeting Lindberg, the Sims came away thinking they could make their own garden, learning from Lindberg’s experience. Brainstorming with the Urban Ecology Center, Growing Power, and the Victory Garden Initiative led to the current Future Green project, which Lisa Sim said is still a guinea pig. They expect to learn more about what works and what doesn’t in their untested design as the growing season unfolds.

The Sims plan to harvest produce from their rooftop for personal consumption, not for sale. Lisa Sim’s eyes light up when she talks about the day when flowering vines from her rooftop garden will spill over the front of her store’s pale brick façade. But she said their motivation is also broader. “The idea of doing this is to get other businesses excited about growing food,” she said.

That idea is already spreading. Rautmann mentioned a Mequon restaurant is looking into a rooftop garden. So is a Bay View restaurant.

Bella’s Fat Cat owner Mike Schmidt said he intends to build a rooftop garden atop his 2737 S. Kinnickinnic Ave. business. (He was inspired by a YouTube video of Erik Lindberg’s rooftop James Godsil posted to the Bay View Matters list serve and has consulted with both Swee Sim and Lindberg.)

Because Bella’s 5,600-square-foot roof will need reinforcement before it can support a garden, Schmidt said the earliest his garden could materialize is next year. But if it works, Bella’s customers theoretically could be eating burgers topped with lettuce and tomatoes grown just feet away from where they’re served. “We all think that would be great,” Schmidt said.

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