Managing native gardens for fire safety in rural southern Australia

What to plant, where to plant and how to maintain beautiful native gardens to make our homes safer during the fire season.

​For more information on this topic have a look (and download the PDF) at the CFA’s very useful booklet on Landscaping for Bushfires - Garden design and plant selection

Planting native gardens with groundcovers, shrubs, and small trees for fire safety and aesthetics

Living in the country has a lot going for it most of the year – plenty of wildlife, cheaper property prices, great communities, less traffic and clean air. Then the summer rolls around and the frightening prospect of bushfires becomes a sobering reality once again.

Bushfires can be deadly as we all know too well, and they are going to become more frequent and more serious in the southern states according to the Climate Institute’s long term projections 

www.climateinstitute.org.au/verve/_resources/2016_Bushfire_Factsheet_-_FINAL.pdf

Public enemy number one in the bushfire season, aside from hot days with strong northerly winds, are the plants that burn and carry the fire to our homes - grasses, shrubs and trees. Yet we know native gardens often support important communities of native birds, frogs, lizards and insects, give us shelter and a lot of pleasure, so how can we enjoy our gardens and be fire safe as well?

Here are some practical insights into what to plant, where to plant and how to maintain these beautiful native plants to make our homes safer during the fire season.

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Australian plants 'want' to burn.

If you live in the country, you’ll notice that eucalypt trees shed their leaves as the summer gets hotter and the soil dries out. These leaves collect in spouting, on roofs and heap up around the walls of houses and sheds. Gum leaves are also extremely flammable because they contain volatile eucalyptus oils. Some gums like the Manna Gum, Eucalyptus viminalis, also shed ribbons of bark in the summer that build up on the ground around the trunks of the trees along with the leaf litter and small branches. This is because gums and many other Australian plants need fire to reproduce. Fire aids seed germination and dispersion, as well as providing a chemical rich ash bed that is critical for the seeds of some plants to germinate.

As gums are an attractive landscaping feature and an important food source for wildlife, it is desirable to include them in gardens around buildings, however it is safer to plant small gums with smooth bark to minimise their likelihood of burning. Examples of small smooth bark gums that are suitable to plant in gardens near the family home and outbuildings are Cup Gum, Eucalyptus cosmophylla, Fuschia Gum, E. forestiana, Wallangarra White Gum, E. scoparia, Snow Gum, E. pauciflora, Platypus Gum, E. platypus.

Gums are members of the Myrtle family and so are Bottlebrush (callistemon), Tea-tree (leptospermum), and Honey myrtles (melaleuca), which also have aromatic oils in their leaves and are all very flammable. These plants are safer planted a distance of at least twice their mature height from the walls of a house. Gums taller than 10 meters are safer if planted well beyond 20 meters from the home because of their summer habit of  shedding leaves that can blow tens of meters in strong winds, adding to fuel loads around rural buildings.

Are there fire retarding plant species?

You may be wondering if there are native plants that are not flammable, that will protect a house from fire. This is a question that I have grappled with for years, and the answer is yes and no.

Yes, because many of the hardy natives from the acacia (wattle), banksia, casuarina (sheoak), correa (native fuschia), dodonaea (hop-bush), hakea, grevillea, prostanthera (mintbush), rhagodia (saltbush) and westringia (native rosemary)genera’s are less likely to burn than the myrtles discussed above, if they are young and healthy or are older plants that are regularly pruned. 

No, if they are old and woody with dead wood on the interior of the plant. Any plant will burn if it’s in this condition, and any plant is more likely to burn if it is drought stressed from weeks without rain. Even succulent shrubs without aromatic oils in their leaves like Hop Goodenia, Goodenia ovata will burn if they are old and woody.

The good news is that all native plants, including the aromatic myrtles, will reduce wind speeds and shield a house from radiant heat. Both of these characteristics will critically improve your likelihood of surviving a fire and are very valuable assets

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Prune native shrubs back, up to one third, in the autumn/winter/spring
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Pruning to reduce old wood, remove dead wood and encourage fresh new succulent growth in the summer, reduces their likelihood of burning in a fire situation. Pruning off the lower branches of native shrubs and small trees will reduce the risk of fire climbing into the shrub in areas mulched with wood chips or leaf litter. These are standard pruning practices to keep a garden looking at its best.

Tussock grasses like the popular Silver Tussock Grass, Poa labillardieri dry off in the early summer and are definitely a fire hazzard. This can be managed easily by burning them with a flaming rolled up newspaper before the fire restrictions are declared or cutting back hard with hedge clippers. This is important maintenance that will keep the plants looking fresh and green over the summer. Lomandras like the Spiny-headed Mat-rush, Lomandra longifolia will stay green in shady gardens and only need cutting back every three to four years. In hot dry prositions cut them hard back before summer when they have a number of dead leaves.

​An open structure in the garden can add to your safety

Keep shrubs well away from the walls of your house
A meter wide path between a garden and the walls of the house provides a good buffer zone and allows access to the house for regular maintenance like brushing down spider webs that can trap dry leaves and glowing embers. Keep native shrubs at least 1.5 times their height away from the edge of the path. Therefore, a 2 m tall shrub should be at least 3 meters from the path's edge.

Space your native shrubs adequately to prevent fire spreading from plant to plant
Native plants that want to burn are a significant risk if planted too near a house, particularly if they are part of a layered landscaping where shrubs are planted very close to taller trees. This creates a ladder of vegetation for fire to climb into tree canopies. Providing a clear space between shrubs and small trees reduces the risk of fire spreading from plant to plant.

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Note: For those of you who are familiar with Sustainable Biorich Landscape design system described on this website, restoring wildlife habitat calls for a different strategy and does not apply when planting within 20 meters your home. Group planting and creating vegetation layers is critical for wildlife but it also increases a vegetation community’s chances of burning in a fire. A cool burn is an important process that restores diversity to a natural environment.

Plant ground-covers that are less flammable, between well-spaced shrubs and small trees

Hardy native groundcovers that are succulent and leafy and no taller than 10 cm will help to suppress weeds while reducing the risk of a fire spreading. Three plants from the Saltbush family and one from the Daisy family look attractive, are low maintenance, and satisfy the above criteria well. The Berry Saltbush, Atriplex semibaccata;​ Nodding Saltbush, Einadia nutans; Ruby Saltbush, Enchylaena tomentosa; and Common Everlasting, Chrysocephalum apiculatum. They can be purchased cheaply as tubestock, are fast-growing and will then spread around the garden themselves, aided by small birds, wind and running water after a heavy summer rain.

Two useful groundcovers that are edible, tough, vigorous, and have large fleshy leaves are Botany Bay Spinach/Warragul Greens, Tetragonia tetragonioides and Bower Spinach, T. implexicoma. Both species will blanket weeds and will certainly stop any fire moving at ground level.
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Strategically placed ponds
A well-placed lily pond can provide a refreshing outlook on a hot day, as well as other lesser known benefits. A pond near an opening window will also evaporatively cool any breeze that happens to be wafting across it. A pond is particularly cooling if placed to the north of the house, as it cools northerly breezes on a summers' day.

Standing water could save your house in a fire by providing a place to quickly fill a bucket or soak a mop. If the pond is topped up on total Fire Ban days, it can become part of your 'fire plan' to protect your home and family.

​Of course, all the birds within 50 meters will come in for a drink and a bathe, adding to the endless fascination that a pond can provide.

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You might also enjoy these articles on planting for bushfire safety:

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Farm plantations can reduce bushfire risk

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Deciduous trees can provide crucial bushfire protection.

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