San Francisco - On the roof of the Glide Memorial Church, gardeners use wine boxes and coconut cores. In Philadelphia, they plant between the roofs of row houses. In New York City, one home owner installed steel beams.
As more people turn to roof gardens to grow their food, they are coming up with all kinds of ways to keep those plots light, and avoid roof sagging and cave-ins.
“Weight is a huge factor,” says Josephine Quiocho, a project organiser at Graze The Roof, a community garden that grows spinach, mustard, kale, peas and other crops on Glide Memorial’s roof.
Graze The Roof has perfected an ultra-light “soil” that includes coconut core and perlite, a volcanic mineral that aerates plants. “The coconut core allows more air into the soil, lightens it up and helps trap moisture. We don’t need heavy, water-clogged soil that can weigh on your roof,” Quiocho says.
The Glide Memorial farmers grow their crops in bread and wine boxes, partly because the boxes are light, partly to show congregants they can grow plants in containers found around the house.
In New York, Lize Mogel took a structural approach: she had five steel beams constructed under her roof so she could begin planting a roof farm this year. Mogel, an artist who has grown roof crops for years, always dreamt of having a roof farm.
“I had to do renovations anyway, so I spoke to the architect and it didn’t cost that much more to reinforce the roof,” she says.
“Because the steel beams will be attached directly to the gratings on which I’ll grow the crops, the gratings can take a massively heavy load. I could raise elephants up there if I want to.”
For urban farmers with weaker roofs, shaving off every kilogram of extra weight is a hobby in itself.
Music teacher Jay Sand, a co-ordinator with the Philadelphia Rooftop Farm, is working with “farmers who want to be architects and architects who want to be farmers” to transform the city’s roofs.
After many hours of study, Sand and his group focused on expanding co-operative efforts across Philadelphia’s famous row houses.
“We decided not to grow on twin roofs, where one brick wall is shared between two houses. For the next growing season, we’re focused on row houses with two brick walls between houses. They are absolutely perfect,” says Sand, a music teacher.
His group is now talking to block captains and residents groups to get more people involved this year.
“I use a light wooden platform to grow my own crops,” says Sand. “If we want to expand the project, we’d like to spread loads between people’s roofs.”
In Chicago, Heidi Hough, who co-writes a blog for rooftop farmers called greenroofgrowers.blogspot.com, has turned her passion for urban agriculture into a search for the perfect lightweight roof garden. Above her home, she grows plants on wooden platforms, which helps take pressure off the roof. A local hot-dog factory also gives her plastic pickle barrels which she “recycles and upcycles” to make planters for vegetables. Hough and some friends have developed an irrigation system that requires little soil and water, vastly reducing the weight of the farm.
“You can buy very good, lightweight irrigation boxes, but we just looked around and copied the system with our own material,” she says.
Hough grows her plants with one 19-litre bucket planted inside another, minimising the amount of water used and reducing the weight on the roof. She uses lightweight peat moss and vermiculite, a mineral often used in soil-less gardens.
Because roof farmers use only as much water as they need, they have to be wary of evaporation.
Hough uses a plastic covering over her peat-moss mix to stop evaporation, while Johanne Daoust, a Toronto roof farmer, uses “shade cloths” she spotted for sale while traveling in China. The cloths block the sun while allowing a free flow of air to the plants.
Daoust says: “Everybody you speak to has their own way of planting those roofs. If you can pick your own breakfast every morning instead of having it flown in by cargo plane, then you are doing it right. As long as you take precautions, it can transform your life.”– Sapa-AP