Fire-Resistant Landscaping

By Cassy Aoyagi | Photography by Lesly Hall

Cassy Aoyagi is the president of FormLA® Landscaping, a Los Angeles-based, LEED-certified landscape design company that has added nearly 1.5 million square feet of native plant habitat to Los Angeles. She serves on the board of the U.S. Green Building Council’s thought-leading LA Chapter (USGBC-LA). Several of Aoyagi’s projects include firewise demonstration gardens. For Flora, she agreed to show us around her own garden in the Tujunga foothills, sharing the features that protect it from wildfire, as well as a few that could still use improvement.

our home base is a little nook adjacent to chaparral, in the city limits of Los Angeles. My husband grew up wandering these mountains and probably knows every trail by heart. He made me love it, even more than the beach where I was raised.

Our garden is our solace, joy, and laboratory. Yet it terrifies those trained to see Los Angeles’ authentic foliage, like our oak trees and desert globemallow (Sphaeralcea ambigua), as dangerous. I don’t blame anyone for misconceptions. For decades, we’ve witnessed non-native hillside grasses like pampas and fountain grasses succumb to fire without understanding our role in placing them in danger’s way. We’ve been mandated to clear “brush” without understanding that the non-native grasses we buy at the nursery become this brush, increasing wildfire danger when they travel to wildspaces where they easily burn. We’ve heard that native plants “need fire” to propagate, as if this need inspires them to create fire. I do hope to dispel these myths.

Our hedgeline serves up an ever-evolving feast.”

To fearlessly love a garden like mine, it helps to understand a few things upfront. Wildfires are spread by embers that fly on the wind, looking for dry fuel. Palm trees and invasive grasses provide it, as do our homes, which are the most combustible and hottest-burning fuel on the landscape. Native foliage, on the other hand? When supported by smart irrigation, that’s hydrated, not the problem some may fear. As for needing fire…native plants do like it, infrequently and as long as things don’t get too hot.

Let’s wander. It’s easier to explain the features of the garden that keep us safe and where the true dangers lie one step at a time.

Every imaginable chaparral shrub wraps our property. We host no combustible, invasive foliage here! Our hedgeline serves up an ever-evolving visual feast of our favorite blooms, fragrances, tweets, and berries. Sunny yellow California flannelbush (Fremontodendron californicum) kicks off the show in spring, followed by California lilac (Ceanothus ‘Frosty Blue’), Nevin’s barberry (Berberis nevinii), and Catalina cherry (Prunus ilicifolia ssp. lyonii). The show never stops.

When appropriately irrigated, this beauty can help intercept flying embers, the most likely source of home ignition. That’s actually a good thing, because hydrated materials don’t readily burn. The tall shrubs’ innate ability to hold hydration in dry summer heat protects us and them. Structurally pruned, biodiverse shrubbery like this also fights disease and infestation that might transform a single-species hedge into tinder.

An expansive native meadow sits inside the hedgeline. In spring, it fills with showy milkweed (Asclepias fascicularis) that fascinates our son, and California poppies (Eschscholzia californica) grown from seeds he scattered as a toddler. In one corner, the meadow slopes toward a deep swale that collects runoff from our slopes and a neighboring hardscape.

The swale and meadow play defense as we enjoy playtime, supporting the garden’s hydration, and offering firefighters safe, distanced space where they can defend our property. The dappled shade of a coast live oak (Quercus agrifolia) and western hackberry (Celtis sinensis) fills with birdsong and keeps the area cool.

Many people see danger in tree canopies. Palms and cypress might combust, however, fire scientists have trained us to value effective tree selection and placement as critical fire mitigation strategies. Thick trunks and branches won’t easily ignite. The oak’s dense canopy resists penetration by flying embers. Even the hackberry’s airy canopy can delay ember travels. Each year, we prune back branches that extend toward the structure of the home, in accordance with the defensible space principles that experts advise.

Any embers tempted to roll toward our home will encounter this defensive shift in elevation and a protective barrier of healthy, hydrated beauty.”

As we evolve our garden, we expand both the canopy and its distance from structures. A young ironwood (Lyonothamnus floribundus) now sits where an Italian stone pine succumbed to structural weakness near the ceanothus. We planted a California sycamore (Platanus racemosa) when we lost a towering eucalyptus. A baby valley oak (Quercus lobata) grows in the hackberry’s shade, ready to succeed it, while a rare Engelmann oak (Quercus engelmannii) sips from the swale.

Beneath the current canopy, we find more protection for our home and hearts. The menagerie of mid-sized, mostly medicinal foliage hides a retaining wall. Here, many species of native, sun-loving artemisia, buckwheat, sage, and mallow intersect with the alumroot, meadow rue, swordfern, and western columbine, which inhabit deep shade. Any embers tempted to roll toward our home will encounter this defensive shift in elevation and a protective barrier of healthy, hydrated beauty.

Nearer our home, low-growing foliage tickles our ankles. It also tickles us to know that the healthy, hydrated native plants will inhibit and even smother rolling embers. We hear the crunch of gravel beneath our feet. While expanses of gravel present too great an opportunity for embers to move freely, our small gravel patios form a useful defensible space for flammable furnishings and other creature comforts. Permeable concrete patios host lounge chairs and meet our sliding glass doors.

Should firefighters need to fight a home ignition point, they have this additional defensible space.

Behaviors are important too, and some of ours are respectable. We placed hydrated foliage between the neighbor’s wood fence and our home. We chose furnishings with no cushions, no umbrellas, often the most flammable items in a garden. We need no gas-powered equipment for maintenance, so we are free of related sparks and fuels. We consistently take protective actions like relocating or removing foliage that fails, structurally pruning shrubs, and raking debris from gravel.

Now that we’ve discussed our defenses, from the ember-intercepting tree canopy and hydrated hedges to our proactive choices that lead to smart behavior, let’s tour the greatest dangers on our property: our creature comforts, our behaviors, our beloved windows and wood.

Day-to-day, we behave imperfectly. Our son brings his toys in, but we leave a rope swing hanging from the oak. We keep tools with wooden handles lined up against the garage—negligent!

We hesitate most when it comes to addressing our greatest dangers. Our wood siding and window frames will easily burn if embers collect and build heat against them. Heat could melt the expanses of single pane windows, inviting embers inside. Replacing these features would require rebuilding entirely, leaving nothing of our historic structure. We did replace the roof with Class A materials—but only when it began to leak. As a society, better building materials and design practices must play an important role in “hardening” our properties to wildfire.

Now that you have the full picture— our garden, our home, our behavior—perhaps you see that the danger is me, is us. Human activities hold responsibility for 95 percent of wildfire ignitions. Our choices, from where and how to develop, build and plant to whether or not we put our toys away when we are done with them, determines the availability of combustible fuel. Authentic nature, effectively maintained and supported, mitigates the danger we create for ourselves. The sooner we realize that, the safer we’ll be.