Green roofs – improving urban environments in a changing climate

Partners: Melbourne Water, Department of Sustainability and Environment, City of Melbourne, Committee for Melbourne

Researchers: A/Prof Nick Williams, A/Prof Stefan ArndtA/Prof Kath Williams, Dr Nigel Dunett, Dr Claire Farrell, A/Prof John Rayner

Funding: Australian Research Council Linkage Grant (2010-2013)


In 2010, green roofs were an emerging climate change adaptation technology that was widespread in Europe and North America, but rare and untested in Australia.

In this project, we investigated green roofs in Australia, challenges to increasing their use and major information gaps that needed to be researched to progress the industry in Australia.

Key findings and recommendations

  • The ideal species for green roofs were high water users which were also drought tolerant.
  • Survival is determined by substrate properties, leaf succulence and plant water use.
  • Plant survival was greatest in substrates with higher water holding capacities.
  • Plants with low water use and high leaf succulence survived longer.
  • Both additives, silicate granules and hydrogel, increased plant available water but only silicates increased time until wilting. Silicates also increased plant growth. Silicates were effective in both substrates (one based on scoria, the other based on crushed terracotta roof-tiles) despite differences in air-filled porosity. Silicates could be used to improve plant establishment on green roofs where water is limiting.


Farrell, C., X.Q. Ang and J.P. Rayner, 2013a. Water-retention additives increase plant available water in green roof substrates. Ecol. Eng, 52: 112-118.

Farrell, C., R.E. Mitchell, C. Szota, J.P. Rayner and N.S.G. Williams, 2012. Green roofs for hot and dry climates: Interacting effects of plant water use, succulence and substrate. Ecol. Eng, 49: 270-276.

Farrell, C., C. Szota, N.S.G. Williams and S.K. Arndt, 2013b. High water users can be drought tolerant: using physiological traits to improve green roof plant selection. Plant Soil, DOI 10.1007/s11104-013-1725-x.

Williams, N.S.G., J.P. Rayner and K.J. Raynor, 2010. Green roofs for a wide brown land: Opportunities and barriers for rooftop greening in Australia. Urban For. Urban Green., 9: 245-251.


For more information please contact Nick Williams from the Green Infrastructure Research Group at

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