The firewise garden
Plants and strategies to make your garden less flammable in a bushfire
All plants burn. So do most houses. But in a fire-prone area, what we plant in our gardens, and what we build, can be a matter of life and death.
A key recommendation from the 2009 Victorian Bushfires Royal Commission, established in response to the Black Saturday bushfires that killed 173 people and destroyed more than 2000 homes and gardens, was the need for guidance on fire-resistant garden design and plants.
Two years later, the state’s Country Fire Authority (CFA) provided information and advice in a 64-page online publication called Landscaping for Bushfire: Garden Design and Plant Selection, in which plants are described as being either fire-resistant or fire-retardant. A fire-resistant plant will survive fire but may be highly flammable, whereas fire-retardant species burn slowly or may be slow to ignite.
At this point it’s worth repeating that, while various plants respond differently to fire, all plants burn! Still, some plants are, to use CFA’s terminology, firewise. The species you use and how you display them will depend on your soil and climate, and more fickle things such as personal taste.
balancing void & mass
There are some basic design principles that help to protect homes and gardens from fire, including breaking up the continuity of vegetation. In the jargon of William Guilfoyle, who designed Royal Botanic Gardens Victoria, Melbourne Gardens, that means creating large voids of lawn between the areas of garden mass.
To entirely fireproof your home, a field of concrete or a well-kept lawn stretching up to 50m from your home would be best. But few of us want to live with that outlook. Better to move into an apartment and turn your back on the beautiful bushland.
Adding a little risk, but not too much, you can include some well-spaced trees. Choose species that have smooth bark (but not bark that will ribbon and flake in summer, such as that of manna gum), as well as an open canopy and not much leaf drop in summer. Prune off the lower branches for good separation between the ground and the canopy.
leaf ammability
Plants with large, fleshy leaves are likely to be more fire-retardant. The more water in the plant, the better. What you don’t want is oil and waxes.
Most species in the families Rutaceae or Myrtaceae – the former including boronias and murrayas, the latter eucalypts and melaleucas – are likely to contain flammable oils, so it’s best to avoid these. That said, citrus (Rutaceae) and lillypillies (Myrtaceae) are often recommended, presumably because they have less oil, or less-flammable oil. The heaths, in the family Ericaceae, can be very waxy, and are therefore prone to burning.
Good trees to consider are crepe myrtle, brachychiton, strawberry tree, fruit trees and figs. My favourite garden tree, Persian ironwood (Parrotia persica), has the winning trifecta of deciduous leaves in autumn
(and little leaf drop at other times of the year), smooth bark, and an open canopy.
Consider rainforest plants, too, including proven performers such as pittosporum and lillypillies. Avoid the common sweet pittosporum, as this is an aggressive weed, and it’s also quite flammable when dry.
Some dryland wattles, such as the silver mulga (Acacia argyrophylla) and sandhill wattle (A. ligulata), have fleshier leaves and seem to be more fire-retardant.
tidying up
What you do around trees and shrubs is also important. Mulch keeps plant roots cool and moist in summer, but most of the best and most attractive mulches are flammable. Not all of us want to use gravel or scoria. As a compromise, keep the mulch layer slim, which is probably best for water penetration anyway, and don’t lay it fresh during summer.
Keep grass cut relatively low, albeit in opposition to what you might want to do to save water. Look for a compromise. The CFA guide suggests keeping lawns no higher than 5cm near the house and 10cm further away. General garden maintenance helps, too. A rambunctious and unruly garden might be good for the soul, but it’s also good for the spread of bushfire.
When choosing groundcover plants and small shrubs, those from saline areas are a good place to start, particularly if you live in a coastal area. Saltmarsh plants often have fleshy leaves, possibly to dilute the salt in the soil, and the salt itself might be a fire retardant. Consider boobialla (Myoporum spp.), eremophila, chenopod and pigface for your garden.
cost bene t
I’ve focused here on Australian plants because we tend to think of them as quick burners, but the basic principles apply to any plant in your garden. I like the very practical advice on the website of the Australian Plants Society (Victoria): “When fire restrictions permit burning off, throw a small sample of foliage from each tree and shrub onto a fire and see how much it flares up. Consider removing plants with foliage that flares fiercely.”
In the end, as with the choice of living in a bushfire-prone area in the first place, what you grow in your garden reflects the risk that you and your community are willing to bear for enjoying the beauty and health benefits of the bush. Select and plant carefully, but remember, all plants… and you know how that ends.