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Some thoughts on the fire resistance of California native plants in your garden

October 14, 2023

Nancee Wells, a field guide in the Dana Point/Laguna Beach area, sent me an email asking about the fire resistance of California native plants. Although California natives will eventually go up in flames in a major conflagration as all plants do, the fire resistance of many native species is significant. In the words of Bert Wilson, the legendary founder of Las Pilitas Nursery: “A watered apple tree leaf burns faster than an unwatered Ceanothus leaf.”

Wilson’s research showed that samples of detached leaves of many California natives that went an entire summer without water took longer to ignite than the leaves of non-natives that had been regularly watered. The reason for this is that many natives have leaves that are small and leathery, characteristics that impart fire resistance. In a flammability test conducted by Wilson in September of 2005, following a series of 90-degree days, the leaves of a large number of California native species that had not been watered all summer took more than a minute to ignite. Among these, Ceanothus species in general, and Ceanothus ‘Wheeler Canyon’ in particular, were singled out as particularly fire resistant with the suggestion that they could potentially serve as a “heat shield” in our landscapes.

Wells inquired about the fire resistance of certain widely planted California natives, with toyon being foremost among them. In the manner of many California natives, the aerial portions of the plant will catch fire without the whole plant burning to the ground. And regardless of how much it burns, it will probably not die in a fire, with fresh shoots growing up from the charred base of the plant soon enough. The name “toyon” was given to the plant either by the Ohlone, a native American tribe in central California or by Spanish explorers in the 1800s, since “tollon” is an old Spanish word for “canyon,” a habitat amenable to toyon’s growth. It’s also called Christmas berry or holly berry since its toothed foliage and winter fruit are vaguely similar to those of the classic holly used for holiday wreaths. There are those who say that Hollywood was, in fact, named after this plant which can be seen growing around the iconic Hollywood sign until today.

In 2012, the title of the official native plant of the city of Los Angeles was bestowed upon it. Toyon grows in both sunny and somewhat shady locations, in almost any soil, and can go virtually without water after a couple of years in the garden. Its fruit attracts a variety of birds, as well as coyotes and bears, who consume it voraciously as well. In the first years of the last century, cutting toyon branches for Christmas decoration became so widespread that the state of California, in order to prevent the destruction of the species, passed a law in the 1920s outlawing this practice. The only toyon branches you were allowed to cut were those taken from plants growing on your own property; it’s a law that is still in force.

Wells was also curious about the fire resistance of lemonade berry (Rhus integrifolia). Yes, this plant also burns slowly, taking more than 60 seconds to ignite in Bert Wilson’s test, a time matched by the closely related sugar bush (Rhus ovata). Both plants grow into handsome informal hedges up to ten feet tall, with lemonade berry more appropriate for coastal locations, and sugar bush better suited to our inland climate. The fruit of both species, when pressed and soaked in hot water, makes a tart beverage.

Coyote brush (Baccharis spp.) was another plant whose fire resistance was queried by Wells. The Pigeon Point cultivar used in landscaping is fire retardant, also lasting more than a minute before igniting in Wilson’s test. There is no ground cover more drought tolerant than coyote brush, a group of plants that includes robust shrubs that are much more floriferous than the ground covers. Snow in Summer (Baccharis pilularis consanguinea), as its name implies, is covered with a blanket of white blooms in late June and early July.

Keep in mind that dead growth in any plant is an invitation to fire so make sure you prune your plants regularly if you live in a wildfire area. It is also true that, when all is said and done, the best defense against wildfire damage is a fire-resistant roof such as those clay tiles you say on Spanish-style homes. Your house may have nothing but gravel surrounding it but if an ember or firebrand blows onto your shingle roof, you may lose everything.

In “Firescaping your Home” (Timber Press, 2023) by Adrienne Edwards and Rachel Schleiger, I learned that a neighborhood in Santa Rosa was burned to the ground due to a wildfire that raged five miles away. Firebrands or embers blown from that fire were carried in the wind, landing on the flammable roofs of closely spaced homes that had been considered to be in a fire-safe zone. This book contains a plethora of fire-resistant plant selections, many of them California natives, as well as long lists of plants you should avoid due to their flammability.

As always, do your own research, talk to experts and find out what are the best choices for your particular circumstances.

California native of the week: Bush sunflower (Encelia californica) was the final species whose fire resistance aroused the curiosity of Nancee Wells. Like daisy family members in general, it is noteworthy for attracting beneficial insects, the kind that devour or parasitize insect pests. It is useful for planting on slopes following a fire due to its fast rate of growth and tough roots that prevent erosion on denuded sloping terrain. It grows three to five feet tall with a similar girth and shows off two-inch yellow daisies in winter and spring. Although not long-lived it will self-sow and thus perpetuate its presence in the garden. It is not particular about soil but has allelopathic properties, meaning that it contains chemicals that deter other plants from growing in its vicinity.

To those of you who have encountered wildfires where you live, are there any plants, native or otherwise, that have proven to be fire-resistant? If so, please let me know about them by writing to [email protected]. You can also send questions or comments about gardening practices or problems and your photos — taken with horizontal orientation for possible publication here — are always welcome.

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Orange County Register

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Some thoughts on the fire resistance of California native plants in your garden

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