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Seeds of an edible city architecture

Global warming and food shortages are renewing interest in urban agriculture, finds John Whitfield.

London Yields: Urban Agriculture

Main Gallery, The Building Centre, London 9 April until 30 May 2009

Vertical Gardens

Exit Art, New York City 28 March until 6 June 2009

Radical Nature: Art and Architecture for a Changing Planet 1969–2009

Barbican Art Gallery, London 19 June until 18 October 2009

In Brad Bass's imagination, a visit to the salad bar could become less a chance to load your plate and more a foraging expedition. “I have this vision of restaurants putting up walls, and people picking their own vegetables right off the wall instead of pulling them out of the tub,” says Bass, a geographer at the University of Toronto in Canada.

Sky shoots: Soonil Kim's proposed aerial vineyard for London. Credit: S. KIM, ARCHITECTURAL ASSOCIATION

Something akin to Bass's vision has just been displayed in London. Urban Agriculture Curtain, an indoor, vertical vegetable patch, was installed by architectural firm Bohn and Viljoen at an exhibition on urban agriculture that ran at the city's Building Centre last month. Visitors to London Yields were not allowed to pick their own, but they could eat the exhibit's produce in the centre's cafeteria. Some of the most imaginative ideas displayed came from students, such as Soonil Kim's proposal for an aerial vineyard — with vines growing in barrels suspended from cables — in London's King's Cross neighbourhood. “Students look at the new ground, and they've pre-empted a lot of the current interest,” says curator Jackson Hunt.

Several exhibitions worldwide are surfing a wave of activity in integrating plants and architecture. People have been clothing buildings in vegetation for millennia, at least since the Hanging Gardens of Babylon were constructed around 600 BC. The Vikings insulated their roofs with turf, and the shopkeepers of Pompeii in Italy shaded their balconies with vines. But growing populations, expanding cities, concerns about food security and climate change have given the idea a new prominence.

Vertical Gardens, an exhibition held this spring at New York's Exit Art gallery, highlighted projects for growing plants on and in modern buildings. Examples already built include Patrick Blanc's green wall on the Quai Branly Museum in Paris. Bohn and Viljoen presented a conceptual design for a high-rise tower clad in 'vertical fields', and displayed a mock-up of a balcony offering a view through the branches of an espaliered fruit tree. Dickson Despommier of Columbia University, New York, presented his idea for a vertical farm — a 30-storey tower housing enough animals and plants to produce food for 50,000 people.

Further along the spectrum from architecture to art is a forthcoming show at the Barbican Art Gallery in London. Radical Nature, which opens on 19 June, comments on humans' relationship with the environment rather than suggesting explicit ways to improve it. Attempts to re-imagine cities are not new: Agnes Denes, in her 1982 work Wheatfield — A Confrontation, photographs of which are displayed at the Barbican, planted almost a hectare of New York's Battery Park with wheat in an effort, she wrote, “to call attention to our misplaced priorities and deteriorating human values”. Events on guerrilla gardening and farmers' markets accompany the exhibition.

Grass roots: Havana's urban gardens yield tonnes of fresh vegetables for Cubans every year. Credit: E. DE LA OSA/REUTERS

Green roofs have been installed on new buildings for decades, and the technology and business surrounding them are mature, says Bass, who has studied their environmental effects. Plant-covered roofs, such as that of the refashioned California Academy of Sciences in San Francisco (see Nature 455, 466; 2008), can cut energy bills, reducing the need for both heating and cooling. They mop up pollutants and cool the air above the building, reducing the heat islands that develop in urban areas. And they slow the rate of water run-off, which eases the burden on city drains, thus reducing the risk of floods and pollution of waterways. Well-chosen roof plants may enhance urban biodiversity. If the roof is accessible and can take the weight of the deeper soil needed, you can even grow food up there.

Vertical gardens likewise provide insulation, soundproofing and physical protection to the building's fabric, and they can shade windows, further reducing the need for energy-hungry climate control. They are, however, more complex to build and design than green roofs. Growing plants on a wall, as opposed to trailing them over it, requires a hydroponic system. The plants are rooted in plastic or plant fibres rather than soil, and water and nutrients are pumped into the medium. Although his Urban Agriculture Curtain uses this technology, architect André Viljoen questions the environmental benefits of hydroponic and indoor-grown food. “I'm sceptical about the amount of chemicals and energy used in hydroponic systems,” he says. “And once you start heating or lighting these things, the environmental benefit goes out of the window.”

A better option, says Viljoen, is to weave organic farming into the fabric of a city, inserting market gardens into their patchwork of industrial, residential, recreational and empty land. He has studied Cuba's use of such methods to feed its people after the collapse of Soviet aid. The government encouraged private and communal vegetable growing in cities, and developed a growing system dubbed organopónico, which replaced petrochemical fertilizers with organic ones such as sewage sludge. In 1997, Havana's system produced almost 21,000 tonnes of vegetables; in 2005, that had risen to 272,000 tonnes, and the project has become a flagship for similar efforts worldwide. Viljoen believes that, in the temperate developed world, 30% of a city's fruit and vegetables could be grown within its borders. By reducing food miles, this could yield big cuts in carbon emissions. But for larger reductions, he adds, you would also need changes in diet, as most of the emissions due to food come from the meat industry.

What is needed now, say both Hunt and Viljoen, are pilot projects to test the large-scale potential of green buildings and urban agriculture, which also take into account the health, amenity and aesthetic benefits provided. “Any one argument looked at on its own tends not to be strong enough,” says Viljoen. “But collectively you can make a very strong case.” Such schemes are more likely to come from the retrofitting of existing spaces and buildings than from high-tech, high-concept projects, says Hunt, as people green their own environments and pressurize local government to do the same. “There's a groundswell of interest in the subject, but developers are very conservative by nature,” he says. “If it's going to happen it's going to be community-driven.”

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Whitfield, J. Seeds of an edible city architecture. Nature 459, 914–915 (2009).

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