Drought tolerance and fire resistance don't go hand-in-hand

Since assuming stewardship of my garden over fourteen years ago, I've focused on selecting plants for drought tolerance.  In the early years, that effort involved eliminating water hogs like the lawns that originally blanketed more than half the garden, filling the empty space with far less thirsty plants and beds divided by flagstone paths.  Unfortunately, a plant's drought tolerance signifies nothing about its fire resistance.  The swarm of fires that tore through Southern California in January, decimating the communities of Pacific Palisades and Altadena among others, shone a flood light on the dangers posed by wildfires, which have grown both more frequent and more intense over the years as a result of climate change.  In mid-February, the Los Angeles County Board of Supervisors adopted an ordinance calling for the creation of "defensible space clearance" surrounding homes in areas facing significant fire risk.  Cal Fire, formally known as the California Department of Forestry and Fire Protection, in turn issued new fire hazard maps, extending the vulnerable areas in Southern California by 3.5 million acres.  The Cal Fire map isn't helpful to us because most of our peninsula is under "local authority" jurisdiction and therefore not reflected in their map but my city's own map shows that our entire city is designated at severe risk.  I should note that our peninsula hasn't experienced fires with the scope or destructive power we witnessed in January.  However, my in-laws lost their home in Malibu to a massive wildfire in 1993 so my husband and I sensitive to the impact these events can have.

The Los Angeles Fire Department will be conducting inspections, probably in June in our coastal area.  These have been conducted annually in the past and we've never received a warning of any kind but, given the notice we received several weeks ago citing the new ordinance, there's reason to believe that this and future inspections will be more rigorous.  Among other things, the notice of homeowner responsibility includes the following:

"It is required that all trees and shrubs shall be maintained free of deadwood and litter.  Native and ornamental vegetation known to be flammable, including, but not limited to: Acacia, Cedar, Cypress, Eucalyptus, Juniper, Pine, and Pampas Grass shall be removed within 30 feet of any structure..."

Failures to comply with inspection findings within thirty days are subject to fines (on top of an annual inspection fee).  I sought to get ahead of the game by conducting my own research.  As there's no master index of "flammable" plants, making those determinations isn't easy!  I pulled a number of lists off the internet.  The most useful was one published by Marin County, which provides a list of fire-prone plants as well as those that are fire resistant.  (You can find a copy here.)  Most other lists were less comprehensive and many contradict one another.  I also discovered that there are few sources that provide ratings of the many plants native to South Africa and Australia I've used in my garden.  I relied a lot on AI-generated summaries, although those can provide fuzzy guidance.  I met with my arborist on Monday to review my working list and solicit his input.  At present, I'm planning to remove roughly twenty-five plants in advance of the Fire Department's inspection.

The reference to Acacias in the Fire Department's notice hit me like a sucker punch.  I've no Acacia trees but I have quite a few 'Cousin Itt' Acacia cognata shrubs.  I've come to terms with removing those closest to the house.

These are 2 views of a single fluffy Acacia 'Cousin Itt' at the base of tree-sized Leucadendron 'Pisa'. They sit directly outside my home office.  'Pisa' is a hybrid Leucadendron.  While some Leucadendrons are said to be fire resistant, when I looked into 'Pisa's' parentage I learned its parent is L. floridum, which was pronounced highly flammable.  Noting that it hangs on to its vast number of dry cones, it's on the list to go with the Acacia.  I will mourn the loss of both.

The Acacia 'Cousin Itt' shown here sits outside our living room and catio.  The Salvia lanceolata growing up through its middle, although not flammable, will also go.  My purpose with the latter removal is to facilitate my replanting of the empty area.

I'm not removing the two masses of these plants further from the house, although I recognize that I could be ordered to do so following the inspection.  As I understand it, the principal problem with this Acacia is the deadwood they develop below that fluffy foliage and the debris they drop.  I've made it a practice to cut back the deadwood and regularly rake the debris in the hope that may be sufficient.

These are 2 views of the 3 'Cousin Itt' Acacias massed aeound the base of a peppermint willow (Agonis flexuosa) just inside the Xylosma congestum hedge that encircles the back border of the garden.  The Xylosma itself is considered fire resistant.

2 more 'Cousin Itt' Acacias sit beneath a strawberry tree (Arbutus 'Marina') in the front garden.  The photo on the right shows the flowers the plant produces.  The shady area behind the Acacias slopes down in the direction of another section of Xylosma hedge,

My Hong Kong orchid tree (Bauhinia x blakeana) isn't reputed to be highly flammable but of late it shows clear signs of impending death.  The arborist was also concerned and noted signs of what might be insect borers.  I elected to remove it.

While the tree normally drops brown folded paper-like leaves in summer's heat, I don't recall a massive loss of leaves during our cool season, especially when the tree is still flowering.  It looks awful and the leaves look like dry debris to me, much of which gets caught inside the Pittosporum and breath of heaven (Coleonema album) shrubs below.

The red powder puff shrub (Calliandra haematocephala) isn't generally considered highly flammable, although its flowers can be.  However, the four shrubs I inherited as foundation plants next to the garage and house have been treated as hedges, regularly sheared to keep them neat and out of pathways.  That's not how these plants were intended to grow.  Given sun and sufficient space, the branches grow outward in a vine-like manner and bloom abundantly.  Placed against walls under rooftop overhangs and sheared almost monthly, they flower little and collect endless amounts of dry litter.  I've elected to remove all four of them.

There are 2 Calliandras planted against the front of the house with a single Pittosporum tobira planted between them.  Although the latter is fire resistant, this is another case in which I've elected to remove it along with the 2 Calliandras in the hope of creating a more cohesive landscape in this area.  Tentatively, I'm thinking of replacing all 3 shrubs with succulents.

I'm particularly sad to remove this Calliandra because it's the most reliable bloomer in the bunch.  It's a narrow bed, probably destined to be filled with succulents.

The only negative associated with removing this Calliandra shrub at the back of the house is that it hides the wiring at the back of the television sitting next to the window.  We can pull one shade down but I'm hopeful we can find a more attractive solution at some point.

The dried leaves and fallen litter of Jacarandas is considered highly flammable.  While that can probably be managed, the dwarf Jacaranda 'Bonsai Blue' I planted approximately six feet from the house in 2016 hasn't contributed enough to the garden to be worth the trouble.  It's on the removal list.

I love the purple-blue blooms of Jacarandas in flower but it's homely in the spring when its foliage turns a sick brownish color  Also, in 8 years, it's only produced a handful of blooms just once.

My husband expressed concern about the two woody vines growing up an arbor directly adjacent to the roof area of our bedroom.  Neither bower vine (Pandorea jasminoides) nor star jasmine (Trachelospermum jasminoides) are normally considered flammable but the combination of the mass of woody stems they've developed and the dry litter the star jasmine drops on the roof, combined with the arbor's close contact with the roof, led us to put the vines on the list for removal.

My husband plans to remove the arbor itself once the plants are gone

Common rosemary (Salvia rosmarinus, formerly classified as Rosmarinus officianalis) is on most, but not all, lists of flammable plants I reviewed.  One nursery site claimed that the prostrate form is a fire resistant groundcover.  I'm still taking all mine out - and there are a lot of them.

There are 4 large rosemary shrubs in the north-side garden.  (There's also a 'Gold Dust' rosemary shrub in one of the back garden's bed on the chopping block.)

There are many more idling along the path that leads down the back slope.  Those in the photo on the right are a prostrate form that I've found nearly impossible to keep within bounds.

Other plants slated for removal include California sagebrush (Artemisia californica) and heavenly bamboo (Nandina domestica).

The Artemisia (left) is a California native that contains an oil that reportedly makes it highly combustible.  Nandina's dead culms and foliage can make it flammable and my inherited plants haven't been well maintained.

I can't claim to have assessed all the other plants in my garden.  I can't count the number of genera I have, much less the number of individual species.  Also, as previously said, there isn't a lot of data on the non-native plants I have either.  The contradictory assessments in many cases also made me crazy.  Ultimately, properly maintaining my plants, particularly those that produce cones, like Leucadendrons, is probably key to increasing the fire resistance of my garden.  Overall, in reviewing the lists that contained both fire resistant and flammable plants, I was gratified to find far more of my plants were on the first list than the second.

I haven't yet to got a solid date for removal of the plants I've referenced in this post but I've signed off on the estimate proposal.  In the interest of minimizing collateral damage to my springtime garden, I've requested a date in late April or early May.  You can expect to see more succulents when I replant but I don't have any definitive plans at the moment.  I'll probably observe a mourning period.  And then there's always a possibility that additional removals will be required.

All material © 2012-2025 by Kris Peterson for Late to the Garden Party