Fire “safe”?

We hear these catch-phrases all the time:  Fire Safe, Fire Proof, Fire Wise, Firescape. 

They all convey a sense of security – like if we just “landscape” the right way, everything will be ok.  There’s almost a sense in these words that we can simply design landscapes to be fire wise, or firescaped, and ta-da!  Added safety is achieved, everybody goes home happy.   

The trouble is that while we love to use this language, to convey a feeling that we’re all doing the right thing, and that everything is going to be alright in the end, these terms don’t convey what they need to.   They lack accuracy.

Fire “safe” is like deer “proof”.  Those who have lived with deer know what that means.  There’s no such thing.  A young deer will sample just about every plant you have, leaving stubs in its’ wake.  A hungry deer will eat pretty much everything on the “deer don’t eat this” lists.  Then, if it likes the plants you so thoughtfully grew, it will come back repeatedly unless you lock your garden away in a fortress.  Even then, I’d bet on the deer.  Better to have plants the deer don’t like, and then hope every year is a good rain year so they won’t need to come for your supplemental garden foliage to enhance their banquet.

Likewise, I cannot design a garden to be safe from fire, and neither can anybody else.  There’s no fortress for this.  For every image of a garden left intact after a fire, there are countless others that burned, having done the same things.  Just like there’s no such thing as a plant that is truly deer proof, there isn’t a landscape that is immune to fire.  However, we can mitigate some of the risks by selecting less flammable building materials, laying hardscape in strategic places, avoiding the use of fire magnets, and so forth.  We can reduce many of the risk factors in our gardens and we can harden our buildings so that they are less easily ignited, but let’s stop using words that suggest safety.  The sooner we get super honest about how every little reduction in risk is a good thing, but no amount of them will ever make us “safe”, the better. 

Instead, I like to point out all the many, many ways we can make a property easier to escape from, how to harden a building, how to avoid the majority of pitfalls and work to make and maintain the garden (and structures) more sustainably.  Without sustainability at the core of the work, we aren’t helping to reduce the core reason things have gotten so bad and will continue to worsen.  Without sustainability, we’re just making things worse, no matter what we install.

Jargon sucks

“People don’t care how much you know

until they know that you care.”

-Theodore Roosevelt.

Your client may be one of those who were directly impacted by a wildfire or maybe they know someone who was.  Whether this is your current clientele or not, it still seems important to take the extra few seconds to make sure that your client can see and hear that you care about mitigating the threat to them from wildfires. 

Rather than say ‘let’s create a defensible zone’, take a moment to explain what that particular zone is for, how it works, and what kinds of things will need to happen to keep it defensible.  A defensible zone isn’t just “created”, anyway – to suggest you can make one and walk away is irresponsible.  However, to some clients this may come across as sounding like defensible zones are more expensive and require all sorts of additional upkeep they don’t want to pay for.  They’re not, but by making a big deal about them, you run the risk of making it sound like an extra thing.  Doing work that results in spaces that are defensible needs to be just part of the process of making the right decisions for our clients’ properties, not something additional.  Something integral. Share that point with them and I hope you’ll avoid the pitfalls.

Likewise, when we discuss the flammability or “fire resistance” of plants, we need to be very careful.  No plant is inflammable, and fire resistance has multiple meanings.  Your client deserves the truth and they deserve to be able to trust that you understand the attributes of the plants you are proposing and what that means in the context of fire.  They should be able to trust that you aren’t just picking plant materials from some list without evaluating the appropriateness of those plants for the site, specific conditions around the site, and the changes that will happen over time.

Show them that you care enough to help them keep their landscape responsibly long-term and why that matters, and I bet you’ve got a start at something worth defending.

Conduction, Convection, & Radiation

When material ignites from proximity to a heat source, it comes from convection, conduction, and / or radiation.  The example below is often used and the materials are familiar to most people, so it is a terrific way of explaining to clients. 

Conduction:  Get an imaginary candle and an imaginary match (hey, I’m not going to tell you to start a fire – my insurance would kill me!)  OK – now imaginarily strike the match and light the candle.  Did the matchstick burn your fingers?  I hope not – that’s because it is made of wood or cardboard or some other poor conductor of heat.  If your candle is in a glass container, the glass might get hot (not all containers are appropriate for candle making btw) and many metals are terrific conductors of heat, I blogged about that way over here but I digress….

Convection:  Hold your hand over the imaginary flame.  Higher.  Do you feel heat rising?  You should.  There are two things happening here – the heat radiating towards your hand, yes, but there is also convection: heat rises.  This is huge.  HUGE!  This is the basic information you need to begin understanding how large fires create their own weather and all sorts of crazy things.  My own personal connection to this is that when baking something in the oven, there’s no air being mechanically moved by my ordinary little oven, nothing fancy in there.  But when I open the oven door, all this hot air comes out and literally blows my hair up.  That is convection.

Radiation:  Now hold your hand to the side of the imaginary flame.  As long as you have an appropriate candle container, the sides should be cool enough to handle (conduction) and the hot air is rising upwards (convection), but there’s still heat coming off the flame sideways and all directions.  That heat is being transferred to you by radiation.

I have to admit it took me a while to really get how this information could be applied to my own design work.  I’ll get there in future posts, promise.  Meanwhile ….

Direct contact is not necessary for ignition.  That means you don’t have to hold the lit match flame right on the wick of the candle – if you get close enough and the wick is flammable (as all good wicks are), then the wick will ignite once it reaches its temperature of ignition.  The wick is raised to that level by the transfer of heat through radiation, convection, or conduction. 

This post came about because I believe that understanding the work of firefighting professionals is key to figuring out how to better design for a fire event.  In order to explore the firefighting world, I took a fire science class at the local jr. college in early 2019.  This was not a class about the landscape at all, but about fire combustion and behavior intended for students who want to become firefighters.  It was somewhat informative; a chunk of the class was about getting a job in the service so that part was fun to watch, but not really my jam.  However, hearing the instructor’s stories about fires and what it is like to be a firefighter indirectly helped me to think up new design challenges and possible solutions that I wouldn’t have had before.  I’m grateful to Lt. Cody, retired Oakland FD for all his tales, academic challenges, and his heart for aspiring fire fighters.

I did not invent the candle example, I’m merely sharing it with you; I’ve included a link for an article I found helpful below.

Mulch is not the enemy - part 1

Google any combination of the words mulch, flammability, risk, and so forth and you’ll find oodles of articles with frightful headlines talking about people being burned by smoldering mulch, mulch being flammable, alternatives to mulch, etc.  If all you do is read the google headlines, you’d think mulch was out to get you.  Please don’t let these articles freak your clients out – they almost always discuss wood mulch as if there is only one kind, and it is the flaming, flying, aggressively-trying-to-kill-you kind.

Look closely at the images in a lot of those posts.  Did you see the same thing I did?  You probably found different articles, so let’s find out:  I saw a lot of shredded mulches (which are easily ignited with a high surface area to mass ratio) and I saw a lot of foundation plantings next to flammable siding that comes down low to the ground.  I read nothing about what caused the fires in the example images where a fire happened.  Hmm.  There’s more going on than was addressed in the articles I read.

The benefits of using organically based appropriate mulches in appropriate ways and in appropriate locations outweighs any risk it may pose.  That is why your discernment as a landscape professional is so critical.  You can advise your client in selecting the best options for specific conditions (something I’ll be working on making content for as we go).  Rather than focus on that right now, let’s talk about those perceived risks so you can discuss with your clients.  To be clear, the following are arguments I’ve read against wood mulches used as a protective top dressing in planting areas:

Wood mulch is flammable:  It is unwise to pave or use gravel, rocks, etc everywhere merely to save ourselves from flammability – to do so only makes the underlying causes of climate change worse.  The use of mulch alternatives (such as gravel, etc) where a wood mulch is the better choice can make those plantings more flammable regardless of plant selection.  The problem I see online is not that a top-dressing is made of wood – the problem in most of the articles attacking wood mulch is the use of flammable materials within the 0-5’ zone of a flammable structure, shredded wood mulches, and mulch layers that are too thick.

Wood mulch smolders after the fire is out and can stay hot for a long time:  The safest place during a wildfire is anywhere that has already burned.  In a previously burned area, the fuel has been consumed and a fire has no means of hanging-out there anymore.  Smoldering mulch should be watched in case there is a risk of a flare-up, if it is in close proximity to unburned materials, and because someone could accidentally get hurt.   Mulch that is still smoldering is not a walkable surface without protective gear, and so should not be used for egress paths.  I was shocked to read an article about firefighters receiving burns while cleaning up smoldering mulch.  Were they not taking appropriate precautions?  Did they have on their protective gear?  It didn’t say. 

Wood mulch could blow around:  The speed of wind you would need to lift smoldering wood mulch off the ground and turn it into firebrands is high enough that you should not be there anyway.   To avoid your mulch selection from contributing to an ember shower, use heavy chunky, partially composted mulch made out of recycled, less flammable species.  The heavier the mulch is, the more difficult it is for wind to pick it up, the chunkier it is, the less surface area there is to welcome and hold embers, and if it is partially composted, it will resist ignition better.  See the studies below for more on different kinds of mulches and species of mulch wood.

We have a responsibility as landscape professionals to understand the fears of our clients, be able to address them, and to be able to specify the right mulch for the conditions if mulch is an appropriate thing to do.

Below are two fabulous studies on mulches and flammability.  They use different methods, so both are good to read.  I’d like to address a note or two on each:

The study recommends “not using any organic mulch within five feet of a house located in wildfire-prone areas. Instead, place non-combustibles such as rock, pavers, brick chips or well-irrigated low-combustible plants such as lawn or flowers closest to the house. The more combustible mulches should be used more than 30 feet from the home.”

As landscape professionals, you know that “flowers” is not an adequate description of anything outside what a florist does, so we need a better descriptor.  I once quoted this article (unwittingly to one of the authors) both complimenting the study’s contents and complaining about the use of “flowers”.   I was challenged in return to provide better language. Someday I’ll whittle my response down to less than a novella-sized reply.

I also want to ask why we are using “more combustible mulches” at all!?  Suppose you demo a juniper (highly combustible) or pine tree, cedar tree, anything heavily laden with oils and resins – rather than haul the greenwaste to the landfill where they promote methane generation, it is better to chip them up and spread it to decompose naturally – just not so close to structures and along paths of egress.  Better yet would be to send it away to a composter so that it can come back in a safer form.  I believe that all too often, we chip and spread without considering what we are chipping and spreading.  Where there are options for composting, we should take advantage.

This study concludes: “Inorganic mulches such as decomposed granite, gravel or rocks offer superior fire-proofing as landscape mulches and should be used when mulch is needed that directly abuts flammable structural materials such as siding or decking.”

Given that many existing structures have flammable materials close to the ground (wood siding, deck posts, etc), it would be wise to keep organic mulches from coming close enough to ignite those materials.  Better still would be to add non-flammable skirting to older homes, build decks, fences, and the like with concrete footings extended above finish grade so that wood posts are not in contact with the ground (or use metal posts instead), and so forth. 

Instead, the authors focused on the mulch as the problem – fine, since it was a study on mulch – but rocks and gravels as mulch can become problematic for many reasons, I’ll have to cover that another time.

If you have an additional point that I missed, or was able to explain this in a really clever way to your clients, please let me know!

Talking about Defensible Space

Confession: writing this post makes me a little nervous. It feels like the whole “fire world” is talking about defensible zones and trying to get people to design and maintain them. Here I am, the very phrase “defensible zone” is what I’m going to pick on. I would be lying if I said that I expect it to be well-received. …and I’ll be picking on it again in future blog posts. yikes.

There’s an unintended consequence of calling defensible space “defensible space” without being very clear to our clients about the expectations we can place on it.  For the uninitiated (a great many clients), to say we are making a “defensible space” sounds like not only will the space be defended, but that it will be defended successfully.  It sounds like a guarantee. That is a dangerous impression to spread; it runs the risk of offering false hope and allowing people to behave in dangerous ways during an emergency.  Panicked, stressed people will do panicky things anyway, but if their thinking starts out with errant understanding that they are supposed to be safe, I would put forth that we are doing them a disservice.

Don’t get me wrong, creating and maintaining a defensible space around your property is very important.  Guidelines and requirements vary, but it is an important concept and one that a design or maintenance plan can start with.  That’s awesome.

However, when we talk to clients, it is important to be clear that just having a defensible space doesn’t guarantee a good outcome during a fire emergency.  At a talk I gave in 2018, a homeowner who had lost her home in 2017 spoke to me at the break.  She had clearly done her homework and knew a lot about the prevailing guidelines for this.  My heart went out to her for the story she told – then she said something I shared with the rest of that audience and I share it with you.  I don’t have to paraphrase this, it was a powerful thing she said::

“You can do everything right and still lose your home.”

As landscape professionals working to serve our clients, we owe them the kindness of being clear and gentle with hard truths like these.  Don’t shirk it because it is a difficult conversation. Your clients need to be realistically informed before something happens rather than after.