Plants

Basic Design Techniques and Plant Choices for Growing a Fire Break

Designing for Australian Bush Fires

Before delving into the exciting plants we can use for creating a fire break to try to protect our properties against fires, it’s important to recognise some of the basics of preventing fire problems via design.

  • For reasons that stretch beyond fire breaks, trees—particularly large ones—should be kept a minimum distance away from the house. They should be planted no closer to the house than the maximum height they might reach. This means, if they should fall while aflame, the fire won’t spread to the home.
  • While wind direction can change frequently, knowing from where the prevailing winds come and to what degree can help us place fire breaks in the best spots. Obviously, the best (and only) practice is to prevent from all sides of the home, but in some cases, we can easily recognise the most vulnerable spots and, thus, better protect ourselves.
  • A well hydrated landscape keeps plants lush and healthy and green, which in turn makes them less likely to burn. Of course, we should be working to hydrate the landscape regardless of wildfires, but preventing wildfires is yet another reason to be doing so. Wherever we are, we can design to hydrate the earth.
  • Water is clearly a top consideration when stopping the spread of wildfires, so we want to place our water features—particularly dams—wisely when designing. Having a source of gravity-fed water is immeasurably useful, and placing water features in the line of those spots most likely to succumb to wildfire spread is a highly effective defence.

 

The Crux of Fire Prevention by Plant with a Permaculture Twist

Fig Tree Fire Break
Photograph by stanvpetersen (pixabay)

While there are great lists of plants (including the following one) that can aid in fire prevention, there are some general ideas as to which plants can best do this. Fire-resistant plants generally have one or more of the following character traits: a high slat content, succulent leaves, thick bark, and/or dense crowns. On the opposite side of this coin, flammable plants tend have loose bark, volatile oils, resinous foliage, and/or dead leaves and branches that cling to the plant. Knowing these traits can help us recognise potential allies and ailments to this cause.

Many trees, shrubs and ground-covers prevent fire from spreading, but, in the creed of permaculture design, why not choose ones that also perform multiple functions? That’s what makes the following plants worth highlighting, and most are either native to Australia and can be grown there. Additionally, they all offer edible, medicinal, and/or other productive elements that make them worthy of consideration even for gardens that aren’t necessarily worried about fire prevention.

 

10 Edible/Useful Trees for Fire Protection / Fire Break

Carob
Image by Georges Tsukaïmah from Pixabay

 

Carob trees (Ceratonia siliqua) are evergreen legumes native to the Mediterranean and Middle East. Their pods that are often used as substitutes for chocolate. They can be sown from seed, will generally grow where citrus thrives, but they don’t like soggy soil.

Mulberry trees (Morus sp.) produce lots of fruit, which is delicious for humans and beloved by birds. They are known to be invasive in some places, but they are both drought and salt tolerant. Mulberry can be readily propagated and multiplied with cuttings.

Chestnut trees (Castanea sativa) are high calorie producers, but they are also recognised wildfire survivors. They hold a lot of moisture and have no volatile oils. Chestnuts have the potential for being a staple food.

Cinnamon trees (Cinnamonum camphora) are tropical evergreens, native to Asia, and recognised for their culinary and medicinal uses. They have thick bark, as well as aromatic qualities and lumber potential. They are also drought-tolerant.

Linden trees (Tilia sp.) are throughout the Northern hemisphere. Their leaves are edible (and tasty), their flowers can be made into tea, and they are noted as good for honey production. There are different species, with something suitable for most climates.

Citrus trees are small, evergreen trees that hold plenty of moisture, as well as tolerate drier conditions. Of course, they provide an abundance of food and come in great variety outside of the mandarin-orange genre, including pomelos, grapefruits, and kumquats.

Feijoa trees (Acca sellowiana) are small, evergreen trees native to Brazil, but they have been spread to many places across the world. They provide delicious fruit, as well as tasty flowers. These are great, fire-resistant trees for growing a hedge.

Fig trees (Ficus sp) are another evergreen choice, one that is a good low-maintenance (very little pruning necessary) option with a white latex substance that protects them from heat. There are hundreds of varieties, fruiting and non-fruiting, to choose from.

Fruit trees in general tend to hold water well, thus make good fire-resistant choices. Stone fruits, such as cherries, plums, and peaches, as well as apples and pears can work well where water is available. Pomegranates and quinces are less thirsty.

Kurrajong trees (Brachychiton populneus) are found naturally in Australia, and they have spongy wood, extended trunks with water storing capacity, and seeds that can be roasted and substituted for coffee.

 

10 Edible/Useful Shrubs & Groundcovers

Aloe ciliaris Fire Break
Photograph by tamarale (pixabay)

Aloe (Aloe sp) is mostly recognised for one species, aloe vera, but there are actually many versions of this succulent. Aloe ciliaris (“ground-cover aloe”) is grown specific as a fire break. Aloe arborescens (“candelabra aloe”) get to five feet tall and produce amazing orange flowers. They, too, are medicinal.

Saltbush, or orache, (Atriplex sp) are naturally distributed across the globe, including Australia. Grey saltbush (A. cinerea) has been eaten as bushfood since before recorded history, and old man saltbush (A. nummalaria) is a renowned sheep fodder, erosion preventer, and site rehabilitator.

Wattles, for example Acacia iteaphyla and A. cyclops, are shrubs native to Australia. Like other acacias, they are nitrogen-fixing and evergreen, as well as useful for soil rehabilitation and erosion prevention. The seeds were consumed by Aboriginal people, and the pollen is great for bees and birds. They are known to resist the initial wave of fire, but burn when dried out.

Prickly pears (Opuntia sp), while not native to Australia but Mexico, have been introduced and thrive in arid climates. In Mexico, they are known as nopal, and the pads are used in salads and other dishes. Additionally, these cacti produce delicious fruit. Like the many edible succulents, they hold a lot of moisture and don’t agree with fire.

Globe artichokes (Cynara cardunculus) are short-lived perennials in the same family as thistle, dandelion, and sunflower. They love the Mediterranean region (and are loved right back). They easily grow over a meter high and wide, and they require a good dose of water to flower well for a delicious crop. Sandy soil with a slightly alkaline pH is ideal. They don’t like it too cold or too hot, between 10 – 25 C.

Purslane (Portulaca oleracea), though frequently considered a weed, is both deliciously edible and highly nutritious. Furthermore, it gets its “weed” status for being very adept at both spreading and surviving. It has succulent leaves that squelch fire and will act as a great, low-growing ground-cover if allowed to do so.

Warrigal greens (Tetragonia expansa) are native to Australia and New Zealand, and they are often called New Zealand spinach. They are a perennial vegetable (salad green) that frost-sensitive but heat-tolerant and disease-resistant. They grow quickly and work as a fire-thwarting ground-cover.

Cat mint (Nepeta faassinii) is not true catnip, though cats are attracted to it. It is a fragrant herb, so it can be used in the bouquet garni of companion plants put in the garden for pest deterrence. It is edible and medicinal, as are most mints, and it produces pretty blue flowers that’ll attract pollinators.

Austral seablite (Suaeda australis) is one of many wild and edible Australian plants, and it specialises in growing in saline environments. In fact, it’s an indicator of salinity in the soil and is sometimes referred to as redweed. It has thin, succulent leaves that go red, like the stems, in the autumn. It can be steamed, blanched or sautéed and goes well with seafood.

Australian Bugle (Ajuga australis) makes a great, matting ground-cover that can tolerate frosty, shady, and dry conditions. It’s good for erosion control. It also can deal with polluted environments and just about any type of soil. It’s evergreen, low-maintenance and medicinal, all while providing attractive flowers.

Jonathon Engels

The financially unfortunate combination of travel enthusiast, freelance writer, and vegan gardener, Jonathon Engels whittled and whistled himself into a life that gives him cause to continually scribble about it. He has lived as an expat for over a decade, worked in nearly a dozen countries, and visited dozens of others in the meantime, subjecting the planet to a fiery mix of permaculture, music, and plant-based cooking. More of his work can be found at Jonathon Engels: A Life About.

5 Comments

  1. I teach Permaculture and Firewise Defensible Space Landscaping in the Mediterranean state of California.
    One key component to selecting FireWise plants is ‘how easy is it to maintain?’ For example, the opuntia in the photo has grown so big, one may not be able to cut the grass that may grow under it. (I know it is a stock photo, not yours.) And embers could be hidden under it when they blow in. The University of California fire scientist I have been working with has taught me to look with a critical eye at any plant that can harbor leaf litter and embers when blown in.
    Aloiampelos ciliaris, formerly Aloe ciliaris, forms a thick hedge, wirtrh dead wood hidden inside the hedge and the smaller version https://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=3989 can climb 6 to 10 feet leaving lots of woody growth that needs pruning to stay FireWise, or it will torch from embers flying in.

  2. Nice article. Could you please write another one for fire preventative plants of the southwestern high desert of North America?

  3. Do linden trees kill bees? Reviewing the causes of bee deaths on silver linden (Tilia tomentosa)
    Hauke Koch and Philip C. Stevenson
    Published:27 September 2017https://doi.org/10.1098/rsbl.2017.0484
    Abstract
    For decades, linden trees (basswoods or lime trees), and particularly silver linden (Tilia tomentosa), have been linked to mass bee deaths. This phenomenon is often attributed to the purported occurrence of the carbohydrate mannose, which is toxic to bees, in Tilia nectar. In this review, however, we conclude that from existing literature there is no experimental evidence for toxicity to bees in linden nectar. Bee deaths on Tilia probably result from starvation, owing to insufficient nectar resources late in the tree’s flowering period. We recommend ensuring sufficient alternative food sources in cities during late summer to reduce bee deaths on silver linden. Silver linden metabolites such as floral volatiles, pollen chemistry and nectar secondary compounds remain underexplored, particularly their toxic or behavioural effects on bees. Some evidence for the presence of caffeine in linden nectar may mean that linden trees can chemically deceive foraging bees to make sub-optimal foraging decisions, in some cases leading to their starvation.

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