Whether you are a landscape designer or gardener, or a grower or seller of plants, this timely advice will help your clients in bushfire prone areas reduce the threat posed to them by this natural hazard.
Nearly 80 percent of Australians were affected either directly or indirectly by the 2019-2020 Black Summer bushfires 1. 33 people died and more than 3,000 homes and 7,000 outbuildings were destroyed 2.
The survivability of buildings during bushfires, and of those who occupy and shelter in them, can be significantly enhanced or endangered by the type of plants around the building 3. Well-placed vegetation with low flammability may help protect houses by reducing the amount of radiant heat received by a house, the chance of direct flame contact on a house and wind speed around a house, whilst also deflecting and filtering embers and reducing flammable landscaping materials within the defendable space 3 . However, poorly located vegetation that burns readily may expose a house to increased levels of radiant heat and flame contact.
Designing and landscaping a garden in a bushfire prone area
According to the CFA, landscape design in bushfire prone areas should incorporate the following principles to reduce the threat posed by that natural hazard to property and life 4:
1. Create defendable space
Example: Locate areas of low fuel between the house and the bushfire hazard, e.g. maintained lawn
2. Remove flammable objects from around the house
Example: Use non-combustible, moveable containers and pots that can be relocated in the summer
3. Break up fuel continuity (keep plants separate)
Example: Mown grass provides separation between garden beds
4. Carefully select, locate and maintain trees
Example: Avoid trees with loose, stringy or ribbon bark
Other CFA tips for landscaping in bushfire prone areas include the following:
Use decorative paving, gravel or stone around the house or building to keep plants away from vulnerable parts of the building, e.g. windows, doors
Avoid planting shrubs under trees. Use groundcovers with low flammability and low-growing succulents instead to provide maximum separation between fuel at the ground level and the tree canopy
Use lawn, decorative paving or gravel to provide separation between garden beds. This breaks up vegetation to prevent fuel corridors
Avoid loose, dry mulch
Ensure trees do not overhang the roofline
Create space between tree canopies to help prevent fire spreading from tree to tree. There should be at least two metres between mature canopies
Locate areas of low fuel between the house and most likely direction of a bushfire, e.g. pool, tennis courts, well-maintained lawn or vegetable garden
Recent research commissioned by Hort Innovation through its Turf Fund and carried out by GHD in association with CSIRO assessed the bushfire protection benefits of three common Australian turf varieties: buffalo, couch and kikuyu. The results of this research showed that well maintained (i.e. watered and mown) lawns are not readily combustible under any conditions associated with wildfires unless they are completely dead and have very low moisture contents 5 .
“The turf industry is continually developing new varieties to suit Australian conditions,” says Jenny Zadro, Market Development Manager with Turf Australia, “There are more drought tolerant varieties requiring less maintenance now. Talk with your local grower to find out what is suited to your climate and soils. If landscaping a property adjacent to an area of conservation significance, ask those turf growers to help you select suitable native grass species that are non-invasive.”
Jenny also provides the following tips to landscape gardeners to help them ensure the turf they maintain remains bushfire safe:
Water turf to keep it in a green, live state
Keep the turf cleared of leaf litter and other flammable materials
Keep the turf short - no longer than 100mm
Install the turf correctly to promote a well-formed root system, this will make the turf more likely to retain moisture in dry periods
The CFA says that all plants will burn in the right conditions, even those described as fire resistant or fire retardant. The CFA defines fire resistant species as those that can survive being burnt and will regrow after a bushfire. These plants are resistant to being killed by a bushfire, but not to being burnt. Therefore, they may be highly flammable and inappropriate for a garden in a high bushfire risk area. The term ‘fire retardant’ can also be misleading when referring to plants. It implies that a plant will not burn readily or may slow the passage of a fire.
In bushfire prone areas, it is imperative that you select what the CFA call ‘firewise’ plants. The CFA's online Plant Selection Key can help you determine the suitability of your proposed choice of plants for a garden in a high bushfire risk area. This key is customised to suit Australian conditions. If you are unsure as to whether a plant is ‘firewise’ or not, err on the side of caution. Leave it out and select another more suitable species.
Maintaining your garden
All landscapes require maintenance and those constructed in bushfire prone areas are no different. To reduce the risk of bushfire damaging your client’s properties, undertake these regular maintenance actions as recommended by the CFA:
Clear ground fuel from underneath plants, on and around the house
Prune plants with low-hanging branches, providing separation of at least 2 metres above the ground
Replace plants that die or become diseased
Keep plants well hydrated through watering and mulch
Watering less frequently but for longer encourages the plants to develop deep roots reducing moisture loss during dry periods
Replace or cover organic mulch such as woodchips, straw or dead plant matter with non-flammable mulches
Remove other flammable objects from your defendable space
Remove any fine, dead material that might accumulate in plants
Remove weeds from defendable space as these often contribute to high fuel loads 6
An important caution from the CFA!
While landscape design and maintenance can improve the chances of a house surviving a bushfire, a garden will not provide protection in a bushfire. Leaving early will always be the safest option.
Is your property in a bushfire prone area?
To find out whether the property you are supplying plants to or landscaping for is in a bushfire prone area, click on the relevant link below and search for its address:
NB. Check the relevant state and local planning policies in your home state or territory to find out if additional planning and building requirements may apply to development on your site. For example, the Bushfire Management Overlay planning control applies to high bushfire risk areas in Victoria. This overlay identifies areas where the bushfire hazard requires specified bushfire protection measures to be implemented.
Through this project, three fact sheets have been developed to describe the bushfire protection benefits that living turf can provide, with one each for buffalo, couch and kikuyu varieties. These can be used by the turf and landscaping industries to inform decision-makers about using living turf as part of bushfire preparation and planning.
Ramsay, C and Rudolph, L, 2003 Landscape and Building Design for Bushfire Areas, CSIRO, Melbourne.
Standards Australia AS 3959-2009: Construction of Buildings in Bushfire-prone Areas
Turf Australia 2020, Bushfire protection benefits of turf, Fact Sheet, 30 June 2020