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Australian Natives, Feature Trees, Garden Design, Seasonal Care

Bushfire-Wise Planting: What the Fire Agencies Say About Garden Plants

Pigface, a fleshy native succulent groundcover, spilling over a rock wall with open lawn between the planting and the house

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No garden plant is fireproof. Victoria's Country Fire Authority says all plants will burn under the right conditions, and the Australian Native Plants Society says it knows of no plant that is completely non-flammable. What the fire agencies do say is that some plants are less likely to catch fire than others, and that where a plant sits and how it is kept matter more than its name.

This guide gathers what Australian fire agencies and plant authorities publish on the subject. It is a summary of their advice rather than ours, the sources are linked at the end, and it is no substitute for the advice of your own state fire service or a bushfire survival plan. The CFA is plain about the limits: a garden is only one part of preparing a property, and on Extreme and Catastrophic days leaving early is the safest option.

Quick facts

First principle All plants burn. Aim for low flammability, good placement and steady upkeep
Against the house Paths, paving and gravel rather than garden beds and organic mulch
Trees Plant at least 1.5 times their mature height from the house (CFA)
Look for Broad, soft or fleshy leaves, open branching, tight smooth bark, little dead material
Limit Strongly scented, oily or resinous foliage, stringy or ribbon bark, climbers on the house

Design first, plants second

The CFA's guide, Landscaping for Bushfire, sets out four design principles for any garden in a bushfire prone area: create defendable space, remove flammable objects from around the house, break up fuel continuity by keeping plants separate, and carefully select, locate and maintain trees. CSIRO's bushfire scientists point gardeners to the same four principles.

In practice the CFA's examples include the following.

  • Within 10 metres of a building, keep plants, mulches and fences away from the vulnerable parts of the house, such as windows, doors, decks, pergolas and eaves.
  • Put non-flammable surfaces against the house: paths, driveways and paved areas.
  • Plant trees 1.5 times their mature height from the house, so a tree that will reach 8 metres goes at least 12 metres away. Trees should not overhang the roof or touch the walls.
  • Do not plant shrubs under trees, and keep shrubs in separate clumps rather than continuous beds, so fire cannot climb from the ground into the canopy.
  • Nothing taller than 10 centimetres at maturity directly in front of a window.
  • Near the house, swap organic mulch for gravel, scoria, pebbles, shells or crushed brick. Most garden mulch dries out and burns.
  • Use non-combustible pots that can be moved away in summer.

What makes a plant less flammable

The CFA does not publish a list of safe plants. It publishes a Plant Selection Key, a set of questions that rates any plant as Firewise, Moderately Firewise, At-Risk Firewise or Not Firewise. The key works from characteristics, and they are worth knowing when you stand in front of a plant.

  • Leaves. Wide, flat, thick leaves and soft, fleshy leaves hold more moisture and take longer to catch. Small, thin, narrow leaves dry out fastest.
  • Oils and resins. Crush a leaf. A strong scent usually means oils, as in eucalypts, tea trees, paperbarks, rosemary and lavender, or resins, as in pines. The CFA's advice is to limit these plants and place them carefully.
  • Bark. Bark held tight to the trunk, or smooth bark, is harder to ignite. Loose, stringy or fibrous bark lights easily, breaks off as embers and carries fire into the canopy. Some smooth gums shed long ribbons each year that do the same.
  • Branching and density. Open, loose branching with thinly spread leaves is better than a dense plant you cannot see through. Foliage that starts two metres above the ground is better than foliage that runs from ground to crown.
  • Dead material. Any plant that holds dead leaves, twigs or fronds inside itself becomes more flammable, however it rates otherwise.

The key rates all vines and climbers as Not Firewise, because they add fuel directly to a structure and act as a ladder between the ground and the canopy. Stringybark eucalypts receive the same rating. The Australian Native Plants Society also advises against conifers and trees with rough fibrous or hanging bark.

Plants that appear on published lists

Some authorities do publish lists. State Flora, the South Australian Government's nursery, lists species with low flammability, and the Australian Native Plants Society publishes a long list of plants for fire risk areas. Both attach conditions. State Flora says every species on its list may need maintenance, and the Society says it cannot guarantee that any listed plant will not burn, only that these are more resistant than many others. Among the plants they name:

Trees

Shrubs

  • White correa (Correa alba) and other correas
  • Hop goodenia (Goodenia ovata)
  • Saltbushes, including Rhagodia spinescens and the Atriplex species

Groundcovers and low plants

Where the lists disagree, and why it matters

Read side by side, the sources do not agree on everything. State Flora lists mat-rushes and flax lilies, while the CFA notes that clumping, grass-like plants gather dead leaves among the living ones. State Flora lists two native climbers, while the CFA's key rates every climber Not Firewise. Neither is wrong. State Flora attaches a condition to its whole list, that every species may need excess bark, dead foliage and dead limbs removed, and the CFA's concern with climbers is mostly where they grow, which is usually on the house.

The lesson is that a list is a starting point. Run each plant you are considering through the CFA's key, think about where it will sit, and be honest about the upkeep you will do. A groomed lomandra beside a gravel path is a different thing from a neglected one under a timber deck.

Upkeep is part of the planting

The CFA notes that diseased, stressed or dead plants are more flammable, that leaf moisture is lowest in summer, and that plants are generally most flammable in the mid to late afternoon. Its maintenance list is short and practical.

  • Clear ground fuel from underneath plants and from on and around the house.
  • Prune low branches to give at least two metres of clearance above the ground.
  • Remove fine, dead material that gathers inside plants.
  • Replace plants that die or become diseased.
  • Keep plants well hydrated. Watering less often but for longer encourages deep roots, which hold moisture through dry spells. Our watering guide covers the method.
  • Remove weeds, which often add to the fuel load, and avoid planting environmental weeds in the first place.

If you are replanting after a fire, CSIRO's advice is not to rush. Replant when it is cooler and after rain, and on larger blocks give the native bush time to regenerate by itself.

A word of caution

This page is a guide only. Planning rules, including bushfire overlays and any conditions on your building permit, come first, and they differ between states and councils. Your state fire service is the authority on preparing your property: the CFA in Victoria, the Rural Fire Service in New South Wales, the Country Fire Service in South Australia, the Department of Fire and Emergency Services in Western Australia, the Queensland Fire Department and the ACT Rural Fire Service. A well planned garden helps. It does not replace a plan to leave.

Sources

One more thing before the courier turns up: our guide to what to do when your plants arrive covers the first 48 hours, from unboxing to the first watering, so nothing is lost in the handover.

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