Over the coming decades our parks and gardens are likely to face longer, more frequent and more intense heat waves; unreliable rainfall tending to either drought or deluge; and unseasonably hot days. That's our climate future, even if we manage to halt the damage now. Gardeners are already noting, with a kind of appalled fascination, how climate change is impacting their gardens.
A major, five-year, multi-partner research project called Which Plant Where aims to make greener, cooler and more liveable cities part of our future by identifying the plants that will cope best with a changing climate in the country's five most populous cities.
"We know the importance of urban greening for human health and wellbeing, for moderating temperatures and providing a whole range of ecosystem benefits, but we are increasingly facing issues with climate change," says the project's chief investigator, Professor Michelle Leishman, of Macquarie University.
"The main role of the Which Plant Where project is to give plant practitioners – landscape designers, urban planners, councils, nurseries and growers, as well as home gardeners – a broader range of appropriate and climate-ready plant species, and an evidence base to maximise the benefits and reduce the risk and expense of planting species that won't survive."
The first part of the project collected existing data from a wide range of sources to develop a comprehensive picture of size, growth rate, canopy density, longevity, allergenicity, insect resistance, biodiversity impacts and influence on air and water quality and urban temperatures of 50 plant species. The data will also be used to develop maps of each species' suitability to both current and future climates across Australia.
Two years into the project, the current focus is on glasshouse experiments in which 100 plants are being put to the test for their heat and drought-tolerance. The subject list includes mostly native and some exotic trees, shrubs, ground covers and grasses. On the list are well-known garden options, such as magnolia, as well as those that could be better known, such as the ivory curl tree, Buckinghamia celsissima, a rainforest tree from northern Queensland that has made a successful foray south.
Also being tested are plants that are hardly known at all, but are considered by experts as having great potential for gardens and urban greenspace. One of these is blue tongue, Melastoma affine, named for the effect of its sweet blue-black berries. It's an evergreen shrub to two-three metres that looks a bit like a tibouchina, hence its other common name, native lasiandra.
By 2021, when the project is complete, Which Plant Where will have generated an interactive online database that will allow gardeners – and professional plant people – to identify the plants best able to cope with the environmental changes forecast for the next 50 years, offering more reliable ways of greening our cities.
This article originally appeared in the Sydney Morning Herald on Saturday 22 September 2018.