The performance of native and exotic species for extensive green roofs in Melbourne, Australia.

There is increasing interest in establishing green roofs in Australian cities due to their demonstrated environmental benefits. However, the lack of available scientific data to evaluate the applicability of extensive green roofs to Australian conditions is a major barrier to more widespread use. Relying on European and North American experience and technology is problematic due to significant differences in climate, available substrates and plants. To start to overcome this knowledge gap we evaluated the performance of 9 potential plant species (3 native grasses, 3 native herbs, 2 native succulents and 1 exotic succulent) by conducting drought experiments. Plants were established in green roof microcosms and watered at 2, 5, 10 and 20 day intervals for 160 days. Survival and growth were recorded using digital photo analyses. The native grasses performed poorly as did two of the three native herbs. The two native succulents performed better, but further investigations over longer periods of drought stress are warranted.