Vertical gardens breathe new life into densely populated Asian cities

If plants can grow in the wild on a barren cliff, why not on city buildings, too, French botanist Patrick Blanc, a pioneer of the vertical garden, once mused. He began developing a prototype, and thus began the greening of some of the most densely populated urban areas on earth.

Since his original design was unveiled at the Museum of Science and Industry in Paris in 1988, Blanc's "grown up" green walls have featured worldwide, from Bahrain to Berlin, Tokyo to New York, London to Hong Kong. His projects include one of Asia's largest vertical gardens, at Hong Kong Polytechnic University's Hotel Icon - comprising more than 8,000 plants of 71 species, and completed in 2011.

In Sydney, Blanc is upping the ante, covering 1,100 square metres of the 166-metre high One Central Park tower, the first Australian project by French architect Ateliers Jean Nouvel, in a living tapestry of 23 vertical garden elements featuring 350 plant species. The tower is due for completion next year.

It is his tallest vertical garden to date, but our local architects are not to be outdone. International design practice Aedas, with its largest office in Hong Kong, is building on its green-wall portfolio of two projects already completed: at Gramercy, a 28-storey residential building on Caine Road, Mid-Levels; and 18 Kowloon East, a mixed-use tower in Kowloon Bay. In Mong Kok, Aedas is undertaking one of Asia's largest vertical gardens.

The front "face" of 78-88 Sai Yee Street, a serviced-apartment building due for completion in 2016, will feature vertical plantings 30 metres by 15 metres.

Hundreds of individual pots will be inserted into modules on a steel frame, incorporating irrigation and drainage systems for easy maintenance. The cost of the plantings will be "minimal" and the plants should last "theoretically forever", according to project designer Cary Lau King-hong, executive director of Aedas.

While Patrick Blanc's is a proprietary system, patented in 1988 and again in 1996, Aedas will use one of the many commercially made modular systems that have since been developed.

The design was inspired by the traditional architecture of Hong Kong, especially the iron balconies (many considered to be illegal structures), which have become part of Mong Kok's streetscape. "Historically, many of these balconies were filled with plants as a form of personal garden in the sky," said Lau. "Bringing this concept into our building, a green wall seemingly protrudes from the solid parts of the podium, creating a visual reminder of the historical connection with the balcony."

The green wall also serves to enhance the quality of life for urban dwellers, Lau said. "The setback allows space [for the building] to breathe down onto the street, relieving some of the congestion and replacing it with greenery to have a positive contribution to the neighbourhood."

Elsewhere in the region, living walls are sprouting. Singapore-based WOHA Architects has created, at Parkroyal on Pickering, a building that features twice as much greenery as the nearby Hong Lim Park. The high-end office and hotel tower positively blossoms with a variety of shade trees, tall palms, flowering plants, leafy shrubs and creepers.

Described in architectural circles as a groundbreaking project, it provides 15,000 square metres of sculptured greenery - all designed to be self-sustaining with rainwater irrigation and photovoltaic lighting.

WOHA has earned a reputation for its original and distinctive solutions to the problems of overcrowding, infrastructure and sustainability in Asian cities - but the Parkroyal on Upper Pickering Street, completed early this year as possibly the world's first zero-energy sky garden, is its most ambitious "green" project yet.

Richard Hassell, WOHA co-founder, said: "We're interested in high density as an issue. We are concerned about lost open space, and green space, and we see that as a challenge: how do you build at higher density, but retain liveability? It is important for designers and planners to be thinking about that."

To house populations without consuming agricultural land, cities need to become more dense, Hassell said. WOHA's signature green walls planted in modular systems - custom-built by the landscape contractor - is the firm's way of making cities more dense, but more liveable.

"We are using fairly normal components such as planters but it is the way we incorporate them in the design that is innovative," he said.

While it looks impressive, Parkroyal's expanse of sweeping, cantilevered planting is also hard at work, shading the building and absorbing carbon dioxide. In a climate like Singapore's, the cooling effect of a green wall on a sunlit external wall can reduce the wall surface temperature by 20 to 30 degrees Celsius, Hassell said.

Apart from the environmental benefits, urban plantings also make us feel better, said Hassell, citing biophilia, a hypothesis that suggests there is an instinctive bond between human beings and other living systems.

"Scientists are not quite sure why but it seems to have a measurable effect. People love gardens," he said.

Parkroyal's example has elicited such a positive response in design circles that Hassell is confident the concept will be replicated on buildings across Asia.

It is also in Asia that yet another use has been found for these attractive, industrious gardens in the sky. With a global food shortage looming, they're now being harnessed to sustain the masses, too.

Sky Green Farms opened in Singapore a year ago as the world's first commercially viable vertical farm, producing one tonne of leafy green vegetables every day, which are sold in local supermarkets. It took the inventor, Jack Ng, three years to develop a prototype for high-rise vertical vegetable farming using a system involving multi-layer troughs in rotating, A-frame structures. The system was showcased at the World Cities Summit 2012 as a sustainable method of urban food production.

Ng says his patented system, called A-Go-Gro (AGG), has the potential to produce 50 per cent of Singapore's green leafy vegetable consumption on 50 hectares of land.

"Sky Greens green leafy vegetables are grown in composted soil media, which contributes to good-tasting vegetables, suitable for stir-fry and soups. They are harvested every day and delivered almost immediately to retail outlets to consumers," said Ng.

AGG's modular A-frame rotary system allows quick installation and easy maintenance. Optional automation means troughs can be adjusted for easy harvesting and greater productivity. The space-saving footprint ( two metres by three metres per tower) allows vegetables to be grown on balconies or rooftops. Each AGG tower ( nine metres high) costs S$15,000 (HK$93,690) and can be customised according to weight and height constraints and types of crop.

Big and small, in ways encompassing form and function, urban gardens are flourishing. For greener cities of the future, the only way is up.