High-rise gardening

Forget London's monolithic new Shard, all eyes will surely be on the Bosco Verticale when it opens in Milan at the end of this year. The new skyscraper promises to bring a hectare of forest into the city's central business district, as well as hundreds of new homes. Rather than cold steel and glass, the surface of this high-rise will ripple with organic life.

Made of two towers – one 80m high, the other 112m – Bosco Verticale is currently being planted with 730 specially cultivated trees, 11,000 groundcover plants and 5,000 shrubs. One of the principal architects, Stefano Boeri, calls it both "radical" and an "experiment"; a reaction against the "high parallelepipeds, clad by glass, steel or ceramic" he's witnessed in Dubai.

Big deal for 'biological architecture'

Jill Fehrenbacher, editor of Inhabitat and a follower of architecture trends, says proposals for buildings featuring copious vegetation are increasingly common. "I have yet to see very many of these 'living building' designs become reality, which is why the Bosco Verticale is such a big deal," she says.

The interdisciplinary team working on the project includes botanists as well as engineers. Their research has ventured into testing the wind resistance of certain species of tree in wind tunnels, as well as finding a suitably lightweight substrate able to meet plants' nutritional demands. The residents' needs are also important – trees will be trimmed so foliage doesn't interrupt their views.

Boeri explains that the Bosco Verticale "hands over to vegetation itself the task of absorbing the dust in the air and of creating an adequate micro-climate in order to filter out the sunlight. This is a kind of biological architecture, which refuses to adopt a strictly technological and mechanical approach to environmental sustainability."

Singapore sky gardens

The Park Royal on Pickering hotel in Singapore is another example of a towering building-cum-garden in a dense urban area, but this one is already open for business. WOHA, the architects, says it was inspired by headlands, promontories and planted terraces. Richard Hassell, the firm's founding director, enjoys blurring the distinction between hard architecture and soft landscapes but admits that working with plants is a challenge.

"For architects, it is quite a change in mindset to deal with living things," he says. "Normally an architect is trying to make things that are as static as possible, and resist wear and tear. But plants grow, and change, and drop leaves, and wilt and die if you forget about them."

Over-ambitious?

A 'living building' is never really finished. It will change over time and will require much more maintenance than one without plants. For both the Park Royal on Pickering and the Bosco Verticale, the upkeep will be centralised and carried out by specialist staff. Could such projects be called too labour- and energy-intensive? Jill Fehrenbacher doesn't think so.

"Living plants…clean the air and produce oxygen, they help humidify indoor air, they reduce storm water runoff and the urban heat island effect, and they help insulate a building," she argues. "Even though skyscrapers like the Bosco Verticale inherently use a tonne of resources and energy – simply by virtue of being a high-rise building – all of those trees and plants are going to be beneficial to the building occupants, neighbours and local environment."

And perhaps 'living buildings' have worth based on aesthetics alone. "At the very worst, a garden is a delight to the users, so even if there is minimum environmental value, there is still immense value in having more green spaces in dense cities," says Richard Hassell.

The visual impact of buildings like these can't be underestimated. Apparently Singapore's taxi drivers now make detours to drive past the planted hotel, while Stefano Boeri talks about his structures being "ecology billboards". Jill Fehrenbacher says such buildings will be everywhere in twenty years, as we "try to recreate some sort of primeval garden of paradise in our homes and workplaces".

Future landscapes

More than mere gardens, planted high-rises have the potential to change our cityscapes. "For sure this is an experiment but to have a sequence of Bosco Verticales, to reach a critical mass, this could be quite interesting," says Boeri. "To deurbanise the urban environment is a radical alternative to expensive technology."

The proof of a building's appeal is surely when the architect himself decides to move in. Boeri has reserved himself a small apartment in Bosco Verticale, explaining he's "extremely attracted" to the idea of living high up in these soon-to-be leafy towers of trees.