Unquenchable thirst: The established hanging garden at 1 Bligh Street.

Unquenchable thirst: The established hanging garden at 1 Bligh Street. Photo: Jacky Ghossein

Vertical gardens are a growing trend. But as the industry finds its way amid trades and worksites more accustomed to dealing with metal, steel and glass, it turns out they can be a wilting one too.

Even a garden designed by the "rock star" of vertical gardens, French botanist Patrick Blanc, is not immune.

Blanc's gardens at One Central Park in Chippendale - which will include the world's tallest vertical garden, reaching its 33rd storey - have already undergone replantings since they were installed in February.

Foliage hanging along the new One Central Park complex in Chippendale.

Foliage hanging along the new One Central Park complex in Chippendale. Photo: Sahlan Hayes

''There is still a lot to be learnt from all the different stakeholders as to how you incorporate all of these elements without killing them,'' said Hanna Gammon, whose company, Junglefy,was contracted to realise Blanc's vision.

Ms Gammon said the plants at the Broadway site were affected "quite dramatically and quite quickly" when their water source was cut by other workers in October and its alarm system failed.

''We have to educate people about the issues there might be with dust, so that the irrigation systems work and people can't just trample on plants and expect them to survive,'' she said. They are issues likely to strike elsewhere in the City of Sydney, where council estimates it receives about one new application for a green rooftop or wall each week. More than 50 have been approved and are awaiting construction.

The council has developed a policy, now on exhibition, to respond to the gardens' popularity, promote them in the community and address the knowledge gaps in the industry.

The council's senior project officer, green roofs and walls, Lucy Sharman said work still needed to be done developing designs suited to Australian conditions.

"The systems they use in Europe are designed quite differently,'' Ms Sharman said. ''They're designed to be able to withstand snowfalls and spring melts, and obviously we don't need to worry about that too much in Sydney."

Stuart Tyler, the national sales manager of Melbourne-based company Fytogreen, which created the roof garden at MONA in Hobart, said many operators were not doing their research ''and that's our big worry''.

''Guidelines can help in some ways,'' Mr Tyler said. ''But guidelines also require a lot of understanding of the componentry and horticulture that goes into it, and that is still at its learning phase for many people.''

Fytogreen, which created the 40-metre long green wall at 1 Bligh Street, in the central business district, about three years ago, had predicted 75 per cent of the plants initially selected for that site would not survive the blustery wind, Mr Bligh said.

''No one had measured it," he said.

He raised concerns that the winds tearing around Central Park's tallest floors similarly risked making short work of its tiny, yet very prominent, plantings.

"If everyone sees a big failed vertical garden, it's bad for the industry," he said.

But Frasers Property, which is developing Central Park, said detailed wind-tunnel testing at the site had informed Blanc's selection of 380 plant species.

The automated alarm systems controlling the irrigation had also been fixed, said Mick Caddey, Frasers Property's development director for the site.

''It would be fair to say that Blanc is the world authority on vertical gardens, and we have a justifiable confidence in his selection of species for One Central Park,'' Mr Caddey said.

"We've had some very high winds on the walls already, with no ill effects to the plants due to wind.''

Clique