Tips to help plan your garden against bushfire risk
BUSHFIRES are a naturally occurring event. Many of our native plants have adapted to deal with this and in fact many rely on fire events as part of their lifecycle.
However development adjacent to bushland areas has increased the risk of fire impacting on people and their assets.
When planning your garden and property for fire protection, it's important to consider plants as an integral part of your overall fire protection plan.
The principles of landscaping for bush fire protection aim to:
- Prevent flame impingement on the dwelling
- Provide a defendable space for property protection
- Reduce fire spread
- Deflect and filter embers
- Provide shelter from radiant heat
- Reduce wind speed
Using fire-resistant plants
No plant is completely "fire-resistant" but some are more flammable than others.
Plants with broad fleshy leaves are better than those with fine hard leaves.
Those with significant amounts of volatile oils, such as the eucalypt family, which includes gums and tea-trees, should be avoided.
The influence of plant shape is a lot more subjective: low growing plants and ground covers are better than shrubs; plants with dense foliage are better than those with open airy crowns; plants which don't retain dead material are better than those which hold lots of fuel; plants with smooth bark are better than those with ribbon and rough bark.
Fire retardant plants can absorb more of the heat of the approaching bushfire, without burning, than more flammable plants.
They can trap burning embers and sparks and reduce wind speeds near your house if correctly positioned and maintained.
Fire resistant ground covers can be used to slow the travel of a fire through the litter layer and fire resistant shrubs can be used to separate the litter layer from the trees above.
If the low flammability plants sound like ornamentals and vegetables and the highly flammable ones sound like dry bush and scrub; then you've got the idea.
The use of trees as windbreaks is a common practice but trees also provide a useful function, trapping embers and flying debris, which would otherwise reach the house.
By reducing the wind speed, a row of trees also slows the rate of spread of a bushfire and a dense foliage traps radiant heat, lowering bush fire radiant heat.
A windbreak that allows 30-60% of the wind to pass through is ideal as less than this becomes too solid with ember laden winds being carried over the top of the break.
To be effective a windbreak must:
- Be located on the side of the lot from which fire weather normally approaches
- Be of sufficient length (generally 100 m minimum length)
- Use smooth barked eucalypts, rainforest trees or deciduous trees
- Make sure there are no breaks of sufficient size to allow winds to funnel through
- Be separated by sufficient distance from the hazard so as not to be consumed and become a hazard itself
To maintain a garden that does not contribute to the spread of bushfires, it is necessary to plan the layout of the garden beds and take an active decision to minimise certain features in favour of other features.
- Maintain a clear area of low cut lawn or pavement adjacent to the house
- Keep areas raked and cleared of fuel
- Use non-combustible fencing
- Organic mulch should not be used in bush fire prone areas
- Planting trees and shrubs such with branches that don't overhang the roof
Plants that have a higher resistance to fire
- Acacia (wattle)
- Ajuga repens
- Acmena smithii (Lilly Pilly)
- Anigozanthos (Kangaroo Paw)
- Atriplex (Saltbush)
- Calodendron capense ( Cape Chestnut)
- Callistemon citrinus
- Canna Lilly
- Casuarina (River She Oak)
- Delonix regia (Poinciana)
- Dicksonia antartica (Tree Fern)
- Eucalyptus maculata (spotted gum)
- Hymenosporum (Native Frangipani)
- Laurus nobilis (Laurel)
- Rhagodia (saltbush)
- Syzygium (Lilly Pilly)