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Rooftop Gardens Might Save Our Wildlife. So Why Aren’t We Making More?

on February 19, 2021 at 5:52 pm under , , ,
Photo: Chrysocephalum apiculatum and other plants next to the standing water - CREDIT: PAUL JEFFERS

Landscape designer Gary Simpson hopes student research on the roof will help pave the way for the introduction of more green roofs in Melbourne because, while this age-old concept has been gathering pace around the world over the past 40 or so years, it has yet to take a firm hold in Australia.

While a number of high-profile living roofs have been established in Melbourne over the past decade – including demonstration and research ones at the University of Melbourne’s Burnley campus – Simpson says the uptake is low compared to many other countries.

“It’s like standing on a beach, watching the tide move in and out,” Simpson says of the ebb and flow of enthusiasm for green roofs in Melbourne. “You get a massive wave of interest and everyone gets excited and then it dies off.”

“We were interested in replicating some of the native structure of grasslands. If you want healthy plants on roofs, you have to look at what happens in the natural world.”

But the unavoidable truth about making gardens on roofs is that they take a lot of planning. A green roof is not the sort of things you can whip up like a raised vegetable bed in lockdown.

Before anything could be done on the roof at Victoria University, a structural engineer was called in to assess its weight-loading capacity. Then five tonnes of concrete pavers were removed and in their place a layer of reinforcing mesh was installed, followed by a plastic drainage cell layer, then a water-retention and drainage layer, a geofabric lining and, finally, a light-weight 150mm-deep growing medium. The garden was framed by a band of gravel to provide extra drainage, and planted with species that were carefully selected to ensure they could thrive in beds of this depth and accommodate the roof’s wind and sun exposure.

It took a large cast of people to get the job done. As well as Simpson, of Infinite Landscape, who designed and built the garden, an engineer, green roof consultant Brod Street, was involved over the course of the project. Two Victoria University academics, Nitin Muttil and Anne Ng, who will help run the garden’s research projects, have also been involved.

Read more: Rooftop gardens might save our wildlife. So why aren’t we making more?



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