Mediterranean Garden Society

Managing bushfire risk in gardens in Mediterranean-climate regions

Hot dry summers with strong winds are the norm in mediterranean climate regions and with these comes the risk of fire. Trevor Nottle in Australia gives MGS the following advice on how to plan to prevent or contain fires on our property and Brian Chatterton in Italy discusses how best to tackle fires when do they occur. Brian’s article is in Journal edition TMG 114.

The photo at the top of this page shows wildfires close to Athens where the MGS garden, Sparoza, is located (Photo Milos Bicanski/The Guardian)

Trevor Nottle wrote about bushfires for Journal editions TMG 101 and TMG 102 and we publish the articles combined here:

Bushfires, wildfires, brush fires and just plain fires are a common feature of all mediterranean-climate regions of the world. Such events are part of the ecosystem, serving to disperse seeds, clean away accumulated dead plant growth and generate renewal by regrowth, flowering and seed germination triggered by heat and smoke. It does seem, however, that these events are becoming more frequent, more intense and more wide-reaching than in the past as we have experienced it. Coupled with a drying climate the risks of the fire season are starting sooner and finishing later too, thus giving property-owners a shorter season in which to prepare for such fires and a longer period over which fire-fighting resources and personnel  have to be stretched. To gardeners and home-owners it is a very worrying scenario for the future. What can individuals do to take defensive action against such potentially devastating events as a bushfire or a wildfire?

Before getting into a panic and rushing about doing ‘something about it’ take a while for a little thought, if only to save doing things which later prove to be a waste of time. Everything depends, as it so often does, on everything else – exposure of the site, prevailing wind directions, whether the garden is new or old. What does the law say about the obligations of property-owners as regards fire prevention? What can you manage to do by yourself or with your partner in tandem to get the work done? How is the flammable dross and over-burden to be dealt with? Where do neighbours come into it? How can plant choices have an impact on the spread of fire? What about hard surfaces and hard landscaping?

Should you have a newly purchased house on a brown-field site, i.e. a brand-new house in a real estate development, you can start with an almost empty palette even if your new property included a landscape package that would set you up in your new home with a turf lawn rolled out back and front, and a foundation planting of several small trees and shrubs. You can pick up on the fire-proofing and retardant aspect of garden planning later as you rework what the contractor has planted.

Example of wildfire defensible buffer zones (LAM tree service, Colorado)

Priority one
The first plan is to have a plan. So make one. If there is a bushfire what will you (and your family) do? Evacuate or stay and defend?

Good advice is available from a variety of sources including the web but sometimes it is possible, just possible, that the information found there may not be especially useful to you in the area where you live, so a better approach is to go to a local source – your municipality, local fire station or emergency services. This will help you to understand:

Priority two
Minimising flammable risks. Put simply, this means getting rid of as much flammable stuff on your property as you can.
The big issue here is taking timely action, in other words action taken well before the onset of the fire season. This means making a determined effort not to acquire an excess of flammable stuff to start with. And if flammable stuff must be kept, it must be stored well away from buildings and from access and escape routes.

Priority three
Having got rid of needless hard rubbish and dangerous substances, you can now focus more keenly on dealing with the dry green waste that builds up on every property, even those that do not know the caring hands of a gardener. This means some kind of maintenance schedule – including for rental properties. Would you rather burn while waiting for the landlord to do it, or do it yourself? It’s common sense really but just look around your own suburb or town to see how many people put it off, or simply don’t do it.

When enough is enough
Can we take comfort from the preventive actions we have already taken, or will our places still burn regardless?

Answering this question is well nigh impossible. Who can say with any exactitude how a fire may develop, wax, wane, roar or whimper and die? Having taken all reasonable precautions, what more can be done? The answer to some of that goes to what local and regional governments do in terms of action, provision of fire services, budgeting and law-making, and some of it will go to what extra steps and costs individuals may choose to bear. An underground fire-proof shelter might be constructed but it won’t save the garden. A far-reaching, powerful overhead sprinkler system mounted on rooftops could be installed but that won’t save the garden as its coverage will be directed at wetting down the buildings, walls and gutters. Every tree within 40 metres of the house could be cut down, as is advocated by some and insisted upon by a few, but the loss of shade would be intolerable to most, and no guarantee against the power of a wildfire. It comes down to a risk assessment that balances inputs – time, energy, money and mental preparedness versus the degrees of possibility that a fire will be catastrophic, extreme, dangerous, controlled or will come in the direction of your place.

That is an assessment that can only be made by you, on the day, according to the advice you receive and the knowledge of what precautions you have taken in the months, weeks and days before the fire threatens.

Bushfires blaze in forest in New South Wales in 2020 (Photo BBC)

Planning in the longer term for changes to what you grow in your garden and for how these plants are organised within a designed space is quite often ignored, especially when home-owners are feeling the pressure to get back to normal as soon as possible after a fire. In gardening terms this means cleaning up and replanting as soon as possible after being burnt out so that they can get on with living life as usual. However understandable this powerful urge may be, it can all too easily lead to repeating the mistakes made in planting and planning the garden in its previous life. To avoid this unhappy experience, consider these matters:

Trees and their capacity to burn or to deflect fire

Palms and cycads: dead leaf fronds and thatch will readily ignite; recovery depends on the intensity of the heat generated and the extent of damage to the growing heart of the plant. Phoenix canariensis (Canary Island palms), Washingtonia filifera (cotton palms) and Washingtonia robusta (Washington palms) must have all dead fronds cut down and removed where possible – some are extremely tall; arborists and professional gardeners have turned this trimming into an art form.

Tree yuccas: Yucca gigantea (syn. Y. guatemalensis), Yucca brevifolia (Joshua Tree), Yucca elata, Yucca gloriosa var. tristis syn. Y. recurvifolia), Yucca rigida, Yucca rostrata and Yucca gloriosa all have substantial skirts of dead leaves which will burn famously unless regularly pulled off with a sharp downward tug, and disposed of in the green bin. Take care to wear stout leather gloves as the leaves have hard, sharp edges.

Kangaroo Island blue gum forest burned in 2020 (Photo Getty)

Deciduous trees: Ash trees, apples and crab apples, maples and sycamores, Crataegus (hawthorns), cherries, pears, Magnolia, stone fruits, almonds, walnuts, pistachios, Cercis, Ziziphus jujuba (Chinese date), quinces, elms, oaks, Lagerstroemia (crepe myrtle), prunus, Celtis, Robinia pseudoacacia (honey locust), Gleditsia, Bauhinia, Melia azedarach, Koelreuteria, pomegranates, kiwi fruit and grape vines will burn but will generally recover, even if only the understock which is shielded from the radiant heat and scorching flames by being underground. Fierce fires can kill the trees outright.

Shrubs that burn:
These include argyranthemums (marguerite daisies), lavenders, viburnum (laurustinus), privet, Escallonia, Cotoneaster, Berberis, rosemary, Echium (Pride of Madeira), phlomis, euphorbias, salvias, lantanas, proteas, leucadendrons, artemisias, Bystropogon canariensis, Cotinus coggygria (smoke bush), Lonicera spp. (honeysuckles), oleanders, coprosmas, senecios, cistuses, roses including species roses and old-fashioned roses, Duranta erecta (pigeon berry), polygala, Arctostaphylos, Baccharis, Vitex, Santolina, Eriogonum, Atriplex (saltbush), Coleonema (diosma), Ceanothus (California lilac), Rhamnus (sea buckthorn) and Pyracantha.

Kangaroo Island blue gum forest regenerating in 2022 (South Australia government)

Fire is an important part of the life-cycle of many of the plants that come from the mediterranean-climate zones of the world in that burning renews plants by replacing old growth with new seedlings, the fire acting both as the means by which seeds are dispersed and as a trigger for germination, while at the same time removing by burning the fuel over-burden that otherwise prevents regeneration of the landscape. Olivier Filippi explains this relationship between plants and fire in his recent book Bringing the Mediterranean into Your Garden (Filbert Press, 2019).

Atriplex nummularia as a hedge at Australia National Botanic Garden visitor centre

Decorative grasses will all burn strongly and so are best not planted in gardens in fire-prone areas. Their main attraction - their ornamental seedheads - is removed by trimming up the dead growth before the fire season starts.

Xanthorrhoea (grass trees, yaccas, blackboys) will burn but are very fire-resistant and will regenerate provided that the fires are not too hot. 

Carpobrotus edulis

Groundcovers that restrict or slow the spread of fire:
Succulents that form carpets such as Carpobrotus, Mesembryanthemum, Delosperma, cotyledons and the red-flowered Mesembryanthemum cordifolium (syn. Aptenia cordifolia) are quite good at limiting the spread of fire if kept free of self-sown grasses and other annual weeds that dry off and present a fire danger. Density of growth is a consideration as some kinds are sparse rather than thick, so a mixed planting of succulents to increase the density of coverage is recommended.

Evergreen plants that are prostrate work well but need room to provide an effective fire break from advancing grass fires. A band of them roughly eight metres wide is regarded as a good distance to plan for. Again, maintenance plays a very important role in fire resistance; all dried weeds and dead growth must be removed, as must wind-blown plastic and paper rubbish trapped in the growth. Plastic-based weed mat is also very flammable, as would be old carpets and layers of newspaper or cardboard used as a base for mulch laid on top. Sawdust and wood-chips are highly flammable and should be avoided where possible, even when prostrate evergreens are to be grown over the top (see below).

Myoporum parvifolium (creeping boobyalla), gazanias, clumping aloes, African daisy (Arctotis*), Eremophila serrulata, ivy geranium, Algerian and English ivies*, Vinca major*, Vinca minor (large and small periwinkles), Berberis aquifolium (syn. Mahonia aquifolium,Oregon grape) and Hypericum olympicum are all distributed as groundcovers in Mediterranean-style gardens and are satisfactory in varying degrees. Some will scorch in extreme heat and exposed positions so placement requires careful observation of the proposed site before planting begins.

Be aware that prostrate rosemaries are flammable due to the high content of volatile oils in the leaves and stems.

Olivier Filippi recommends gravel as a mulch (photo Filippi)

Mulches - vegetable, animal or mineral?
By far the best fire-retardant mulches are those that are inorganic: river pebbles, sand, shell grit, gravel, crushed rock, brick paving, cement paving, slate, stone slabs and (volcanic) scoria. Olivier Filippi (see reference above) writes about making garrigue gardens imitating the natural rock-strewn landscapes of southern France. A garrigue garden is mulched with gravel and stones. He proposes that after fire the garden will recover by seed regeneration as does the wild landscape. The idea is interesting but would be a challenge to those trying to remodel an Anglo-European garden to be more fire-resistant.

Vegetable and animal composts will all burn, including pine bark, sawdust, forest mulch and spray on mulches. Very intense fires generate enough heat to incinerate all the organic material in the soil, leaving behind white sand or small clay particles.

Lawns and their place in fire management
Well-kept lawns, watered and green, can considerably slow the rate of spread of ground fires. It has been suggested that a clear lawn of some eight metres in width can be an effective barrier provided it is frequently cleared of dead leaves, bark, twigs and plastic garden tools, garden furniture, paddling pools and toys.

The proximity and distance of trees and shrubs is always a consideration for home-owners when considering bushfire precautions. For most households it will not be a cut and dried decision to eliminate trees and other growth for a set distance from a house or shed but a trade-off between convenience, shade and shelter, and the possible risks they pose should a bushfire happen. Just as there are some people who like to  live in the bush, there are others who do not want to live anywhere near it, and some who like to be near the bush but not in it  – there are choices and judgements to be made by individuals and families.

However comprehensively you plan, and however mindfully you chose plants and put them in place, there are no guarantees that your efforts will prevent damage caused by bushfires. Bushfires can be retarded or redirected by greenery in their path; that at least has been the experience of property owners in the past, but more recent experience has shaken this handed-down folk wisdom. With the advent of climate change bushfires appear to have grown more intense, larger in scale, more volatile, more violent and less predictable. In many extreme cases the fires seem to have a life of their own, suddenly bursting with unbounded, surging energy that sees treetops in flame hundreds of metres in advance of the fire-front on the ground. This phenomenon is known as a crown fire or a crowning fire.

Pyro-cumulus clouds over the Australian bush (The Times)

Nowadays it is often observed that fires can create their own weather. Huge pyro-cumulus clouds rising many kilometres into the sky generate dry electrical storms which in turn produce thousands of lightning strikes that start spot fires in widely separated areas. Spot fires caused by widely dispersed hot ashes, embers and live cinders are probably the most unpredictable dangers to gardens, even those generally thought to be well prepared. The bad fires of late 2019 saw a new phenomenon develop in extreme fires; this was the pyro-cyclonic winds generated by the erratic, violent updrafts of winds caused by the intensity of the flames. The wind blasts were strong enough to flip 8-tonne trucks over on to their roofs, crushing and killing the fire crews inside the truck cabins. Little wonder then that fire chiefs withdraw their crews from forested areas that, under these circumstances, are simply far too dangerous to work in.  Often described as ‘super-fires’ or ‘mega-fires’, these events are categorised as extreme and disastrous events that are potentially catastrophic and life-threatening.

Fire storm (Bureau of Meteorology/The Times)

Caution is necessary here because while meteorologists and fire investigators are building a body of research it is a work in progress, not yet definitive or accepted as reliable, hence the very contrarian attitudes expressed by politicians, coal industry lobbyists and those broadly categorised as climate change deniers. For lay people, such as most gardeners are, the lack of clarity and the vociferous, combative nature of public discourse just add another layer of confusion to an already uncertain situation. We gardeners can do what we can do, but will it be enough?

The Victorian chapter of the Australian Plants Society published in 2016 a very informative paper on its website that drew on experiences of gardeners in the big bushfires of 2009. It provides a very useful perspective on the range of plants that survived in those fires, which however seem to have been a little less extreme than those of 2019-20 in that pyrocumulus clouds, dry lightning and tornados of flame were not a feature that caused extreme fire storms, as happened in the most recent bushfires.

THE MEDITERRANEAN GARDEN is the registered trademark of The Mediterranean Garden Society in the European Union, Australia, and the United States of America

Data Protection Consent

website designed and maintained
by Hereford Web Design