Fire is a part of Nature, and lightning strikes help to turn over ecosystems by catalyzing new growth and allowing for secondary succession. For thousands of years, Indigenous people used fire as a form of land stewardship to clear out dead plant material, allowing space for new growth and avoiding a dangerous buildup of combustible materials that would have resulted in much larger, destructive fires.  Controlled burning created meadows and grassland habitats for herd animals, which were important food sources.

The influx of foreign settlers and colonialists changed fire patterns: cultural burning practices were prohibited and fires were seen as detrimental and to be avoided at all costs.  Cities were built using flammable materials (mainly wood buildings), and additional human-caused fires disrupted the rate of natural fire events.  At present in Canada, lightning causes approximately 50% of all wildfires, with humans making up the other half.

Western coastal North America is experiencing the worst prolonged drought in 1200 years, and the summers are becoming increasingly hotter and drier.  By the end of the summer, trees are often dried up and hundreds of thousands succumb to the heat stress or in their weakened state become prey to pests (Mott & Angle, 19).  The mountain pine beetle is the most aggressive and destructive bark beetle in western Canada and the western USA and climate stress is weakening the trees it feeds on (ponderosa, limber, lodgepole and whitebark pines are its preferred hosts).  Long cold snaps will kill the beetle, but with milder winters these are becoming more rare.  The resulting swaths of dead, dried out conifers are ignition-ready fuel (Mott & Angle, 24).

There are three main ignition sources arising from wildfires:  embers/firebrands, radiant heat and direct contact with flames.  Hot, fast-moving wildfires can loft embers for hundreds of meters - even kilometers - ahead of the main fire, and these embers rain down like hail on structures below such as roofs, gutters and yard areas.  Up to 90% of structure fires during a wildfire event originate from falling embers! (Edwards & Schleiger, 65).

Managing the space around the home is typically divided into zones, with varying levels of defensibility.  Closest to the house lies a non-flammable zone, and as one gets further from the structure, zones become less restrictive, although there is always a baseline level of fire resilience practices factored in.  Defensible space is organized into three zones where the density and type of vegetation is closely monitored and maintained.  One can consider a fourth zone beyond those, where habitat is maintained for ecological health (Edwards & Schleiger, 80).

FireSmart BC calls these the immediate, intermediate and extended zones.

Home Ignition Zone. Image credit: FireSmart BC

Zone 1:  0 - 1.5 m «The Noncombustible Zone»

This area also includes any decks and fences that are attached to the main structure.  It should be kept free of vegetation, debris, flammable mulch and weed cloth, and should not contain any items such as furniture, yard umbrellas, garden art and garbage or recycling bins.  Take a walk through your neighbourhood to see how many homes meet the criteria for this inner zone: probably very few, if any!

Zone 2:  1.5 – 10 m «The Lean, Clean and Green Zone»

Grasses, shrubs and small trees can be planted in this area.  Artwork such as sculptures and birdbaths, and furniture (including the cushions) should be made of noncombustible material.  Plants with resins and fragrant oils should be avoided, as they are more flammable than deciduous plants, and herbaceous stems are less so than woody stems.  Gaps of bare ground with fire resistant mulches, rocks or hardscaping create firebreaks, should an ember ignite a patch of grass, for example.  “What if embers fell into this area?” is the question the landscape planner should be constantly considering.  Raised beds and children’s play equipment can be placed in this area near the outer edge, ideally surrounded by bare dirt or gravel.  As with Zone 1, the area should be regularly cleared of debris, and dead plant parts should be removed.

Zone 3:  10 - 30 m, « The Fuel Reduction Zone »

This is where mature trees and more closely spaced shrubs and herbaceous plants can go.  Spacing at least 3 m between tree canopies and following guidelines for vertical spacing and density to avoid ladder fuel situations is recommended.  An open woodpile in this zone should not be immediately adjacent to other plantings.  In high hazard regions, or on sloped terrain, this zone could be as large as 90 m .

Beyond Zone 3, the natural area is often considered habitat area, and is not defensible territory.  Having healthy native ecosystems without a surplus of ground level fuel caused by ongoing fire suppression goes a long way to reducing the risk of large, destructive fires in this area.

When choosing landscape plants for fire-prone regions – the term “firescaping” is often used – selections should be based on plant flammability and suitability for the local climate.

Native plants are typically the healthiest and best adapted to an area.  All plants can burn, but some burn more easily than others. Where you put plants and how you care for them is critical in reducing wildfire risk to your home.  There should be no flammable vegetation, including wood mulch, within 5 feet of the house – the area called the “immediate zone”.  Best practices are to keep this area free of all vegetation, and to cover the ground with gravel, rocks or permeable pavers.

Farther away from the home where plants are located, consider the following questions:

• Does the plant contain resins, oils or waxes?  The higher the level of these, the more flammable the plant, and they also burn hotter.

• Are the plant’s limbs adequately spaced out and balanced or are they packed closely together in a tangled web?  Dense limbs are more likely to trap embers and catch fire.

• How much debris does the plant shed?  (bark, leaves, needles).  Everything the plant drops is potential fuel that needs to be cleaned up. (Mott & Angle, 193)

The characteristics of plants, such as their habit, leaf density and moisture content, along with their health, dictate their susceptibility to ignition. In the Pacific Northwest, for example, one could start with a palette of grasses such as Westcoast bentgrass (Agrostis pallens) and purple needlegrass (Stipa pulchra) which have a high moisture content, less above-ground mass and deeper roots.  In contrast, a popular decorative ornamental such as Pampas grass with lots of feathery, vertical airy growth, is highly flammable.  

Trees planted as specimens and spaced apart can still create cooler microclimates under their canopy.  Fire resistant species in the coastal area of southwest BC (my stomping grounds) include bigleaf maple (Acer macrophyllum), red alder (Alnus rubra) and black cottonwood (populus trichocarpa).  Appropriate pruning up of low branches, removing any climbing vines, and spacing trees apart from understorey species prevents a “ladder fuel” situation where shrubs and smaller trees in close proximity to a large tree catch fire and bring the flames up into the tree canopy, literally providing a ladder for the fire to climb.  Coniferous trees and shrubs are not recommended in Zone 1 or 2, nor the use of their bark chips as a mulch due to flammability.  The ease with which these pitch and resin-laden trees burn is highlighted, for example, by current regulations in multiplex dwellings prohibiting natural Christmas trees as a fire hazard.  To think that in former times, every Christmas-celebrating household had a densely branched coniferous seasonal tree decorated with small actual candles!  And yet, here in my area, houses surrounded by cedar hedges and featuring shrubs right up against the siding are the fashion.

Adding a shelterbelt of well-hydrated and maintained plants can also protect a property from winds and wind-borne embers.  Such a barrier should be semi-permeable to allow some air through and reduce wind velocity on the other side.  Solid walls cause abrupt interruptions in airflow patterns and create turbulence, which can intensify fires and disperse embers over a larger area (Edwards & Shleiger, 93).

Tips to FireSmart Your Home. Image credit: FireSmart BC

There are many regional and provincial resources available with great information on locally native plant choices and tips for fire-wise designing, maintenance and risk reduction.  FireSmart BC has a wealth of information including plant lists, mulch evaluations, landscaping tips and an interactive plant choice tool where you can learn which native plants work best in your region.

Some garden centres and nurseries now add a label with the “Firesmart” designation to their plants for which are good choices for landscapes in higher wildfire risk areas.  

This blog posting merely scratches the surface on the topic of firescaping, but as an entry point to basic concepts and some resources to explore further, it will hopefully prompt you to dive deeper into the topic and learn more about how you can be aware and prepared wherever you live.

References:

Edwards, Adrienne & Schleiger, Rachel.  Firescaping Your Home: A Manual for Readiness in Wildfire Country. Timber Press, Portland, OR, 2023

Mott, Nick & Angle, Justin.  This Is Wildfire: How to Protect Yourself, Your Home and Your Community in the Age of Heat.  Bloomsbury Publishing, New York, NY, 2023

https://firesmartcanada.ca/programs/firesmart-101/

https://firesmartbc.ca

https://www.canadawildfire.org/wildfirefacts

Written by Laurie Smith