Landscaping refers to the location and maintenance of selected plant species around a building to improve its chance of surviving a bushfire. Correctly managed vegetation can provide many benefits during a bushfire including:
- reducing fire intensity
- reducing wind speed
- deflecting and filtering embers, and
- providing shelter from radiant heat.
The following points should be considered when sighting vegetation for fire protection:
- mown lawn or grazed green grass is most appropriate immediately surrounding buildings,
- plantings near buildings should use low hazard vegetation. Plant highest hazard vegetation away from buildings or not at all,
- trees and shrubs should not be planted closer to buildings and powerlines than the distance equal to their mature height,
- space trees and shrubs so that there is not a continuous canopy or line of vegetation from bushland to house, and
- locate well watered fruit trees and vegetable gardens on the side of buildings facing the most likely direction of fire.
Maintaining a zone of fuel reduced vegetation around a building is a good fire prevention measure. This involves regularly cleaning up and removing flammable plant debris before and during the fire danger season. Consider the following maintenance tasks:
- remove trees or prune limbs which overhang the house,
- break the path of fire from ground to tree canopy by clearing debris and flammable vegetation under trees and shrubs and by pruning lower branches to provide a vertical 2 metre fire break,
- remove accumulated debris in trees and shrubs and prune dead limbs,
- retain the moisture content of foliage by watering in the Summer, and
- grow lawn under trees or keep undergrowth slashed.
All plants will burn but some are more flammable than others. The following list groups of plants according to their relative fire hazard:
|High Hazard||Some Native Shrubs||Eg: acacias, melaleucas, callistemons, grevilleas, hakeas, tea trees, banksias|
|Eucalyptus||Eg: Smooth barked varieties are safest|
|Introduced Conifers||Eg: Pines, firs, cypresses, cedars|
|Deciduous Trees||Eg: Fruit trees, oaks, maples, elm, poplars|
|Succulent Ground Covers||Eg: Pig face, strawberries|
|Low Hazard||Salt Rich Plants||Eg: Saltbush, boobialla|
A well-designed and maintained windbreak in a rural area will protect buildings from bushfires by:
- reducing wind speed,
- filtering out flying embers, and
- slowing the spread of the fire.
Wind Speed: When fire winds hit a windbreak they are slowed down and forced up and over the trees, creating a protected area on the leeward side.
Embers: In a bushfire the greatest risk to any home is not the flames but sparks blown around in the strong winds. Trees may catch many of these sparks before they get to the house. Because green leaves contain water, trees do not usually catch fire from flying embers, although this can happen if there is too much dead material in the trees or on the ground underneath.
Fire Spread: Windbreaks slow the wind speed and help slow the spread of fire. They also provide a shield from radiant heat depending on the density of the trees in the windbreak.
Designing Windbreaks: For best results:
- plant multiple rows of trees rather than a single row,
- plant on the sides of the property most likely to be impacted by fire, and
- plant an open windbreak that reduces wind speed without causing turbulence.
Position your driveway on the side of your house most likely to be impacted by fire:
- If you plan to build a tennis court or pool also position it between your home and the expected fire direction.
- Build a stone wall, earth mound, hedge or covered fence close to your house as a radiant heat shield.
- If you are on a steep slope terrace plant your garden with fire retardant species.
- Locate woodpiles away from house.
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. Yet no plant is completely fire-resistant. Some are more flammable than others, but given the right conditions all plants will burn.
There are two basic factors to be considered in determining a plant´s flammability: the first is how readily it burns and the second is how its form influences the way it burns. 'Flammability´ then is, or should be, the outcome of these two factors.
- Plants with broad fleshy leaves and/or high salt content burn less readily than those with fine hard leaves (sclerophyll). Plants with significant amounts of volatile oils, like the eucalypt family (which includes gums and tea trees) should be avoided close to dwellings.
- The influence of plant form 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 that don´t retain dead material are better than those that hold up lots of fuel; plants with smooth bark are better than those with stringy or ribbon bark.
Fire retardant plants can absorb more of the heat of the approaching bushfire without burning than flammable plants. Fire retardant trees can trap embers and sparks and reduce wind speeds near your house if correctly positioned and maintained. Fire retardant ground covers can be used to slow the travel of a fire through the litter layer and fire retardant shrubs can be used to separate the litter layer from the trees above.
If fire retardant plants are to be grown, a firm commitment must be made to regularly maintain them or they may become a fire hazard. This includes sufficient watering so a high leaf moisture content is maintained, the removal of dead material and regular pruning of lower branches. Water availability is likely to be a problem in drier months when the threat of fire is greatest.
All gardeners should be aware that some plants are not wanted in the bush even if they are valued in the garden. Unfortunately there are many ornamental plants that really take off when they get into the bush. Some do so well they choke out the natives, like blackberries, or become a fire hazard, like gorse. Predicting whether a plant will become an environmental weed is not easy so it´s good practice to consult with your local council or the SA Department of Environment, Heritage and Aboriginal Affairs to determine its suitability for your area. Alternatively you could contact your local Landcare or Bushcare Group (Trees for Life) for information on species that are indigenous to your area. They may even supply plants propagated from seeds collected locally.