361 Defensible Space Landscaping Tips

Show Transcript

361 TRANSCRIPT Defensible Space Landscaping Tips

Farmer Fred:

[0:00] Garden Basics with Farmer Fred is brought to you by SmartPots, the original, lightweight, long-lasting fabric plant container. It's made in the USA. Visit SmartPots.com slash Fred for more information and a special discount. That's SmartPots.com slash Fred.

Farmer Fred:

[0:20] Welcome to the Garden Basics with Farmer Fred podcast. If you're just a beginning gardener or you want good gardening information, well, you've come to the right spot. In this episode, we dive deep into the concept of the Wildland Urban Interface, the WUI. It's a critical area where developed residential areas intersect with undeveloped wildland vegetation, and that's often a hotspot for wildfires and destructive home losses. With a staggering amount of housing units situated in fire-prone zones, particularly in states like California, understanding how to protect our homes becomes essential. We talk with Kevin Marini. He's a University of California Cooperative Extension advisor who specializes in landscaping strategies to enhance fire safety. His extensive experience as an arborist and as a defensible space educator make him an ideal guide as we navigate the complexities of yard maintenance in these high-risk areas. Today, it's episode 361, Fire Safe Landscaping Tips. We're podcasting from Barking Dog Studios here in the beautiful Abutilon Jungle in suburban Purgatory. It's the Garden Basics with Farmer Fred podcast, brought to you today by SmartPots and Dave Wilson Nursery. Let's go.

DEFENSIBLE SPACE LANDSCAPING TIPS, Pt. 1

Farmer Fred:

[1:43] Are you familiar with the wildland-urban interface? It's the area where houses meet or intermingle with undeveloped wildland vegetation. It's a focal point, especially for wildfires and the destruction of homes. And this wildfire urban interface areas are particularly widespread in the eastern United States, reaching a maximum of 72% of land area in Connecticut, for example. Now, here in California, we have the highest number of housing units in what's called the WUI area, 5.1 million homes. And that translates to more than 11 million Californians who are living in a wild urban interface, a wildfire urban interface. That means more than a quarter of the state's population is living in a high fire hazard zone. So chances are, and if you ever looked at your insurance bill, you probably already know where you lie as far as wildland urban interface areas, because your rates very frequently are based on that.

Farmer Fred:

[2:49] So you may be thinking, OK, so what do I have to do around my home so that no major problems happen if you live in a wildland urban interface? Well, we're going to tell you about that today. But I'd also like to point out that burning embers are the cause of making the wildland urban interface a much, much bigger area. And I hark back to 2017 in October and the Tubbs Fire, which broke out north of Santa Rosa, which is north of San Francisco, near the mountains. And in that mountainous area northeast of Santa Rosa, that fire broke out. But it created such a windstorm from this fire, there were burning embers, I call them burning pieces of wood, that flew more than a mile westward across a major freeway and into a suburban development of Santa Rosa itself - Coffee Park, where something like 1,200 homes burned, and they were nowhere near a forest. So even though you may see mountains in the distance, don't think you're safe. So getting back to how we protect our home, how do we protect our yard? Let's talk with Kevin Marini. He's a UC Cooperative Extension advisor. We've talked to him in the past about trees and soils because he's a certified arborist. He's a Master Gardener Coordinator, and he's also the University of California Defensible Space Educator. So he is very familiar with this whole idea  of protecting your yard and not necessarily putting in fireproof plants, because as he points out, really, there's no such thing as a fireproof plant. And even though there are plants that you may think are fireproof, well, depending on how you've treated them, they may be, shall we say, dead on the inside and just be waiting to burn because of the way you prune them. We'll get into that. He has a wonderful handout called The Dance of Defensible Space.

Kevin Marini, it's a pleasure for talking with you again. And when it comes to protecting your home from wildfire, it begins in the yard. And in the past, when we've talked about building defense zones that are fire resistance, we've talked about zones one, two, and three. But lately, there's been a new zone added to that, and that's called the zero zone. And what goes on in the zero zone?

Kevin Marini:

[5:08] Well, hey, first of all, thank you so much for having me back on your podcast. I really enjoy this opportunity to do some education and outreach via this medium. I do a lot of talks in person and I do defensible space consultations on site. But being able to reach a huge audience like this is a treat. So first off, thank you for having me. So yeah, I've been teaching a lot about defensible space over the last two years, really for a longer time than that, but really focused  in on it the last couple years. And with that has come this new zone, Zone Zero, as you refer to, called the Ember Ignition Zone. What's interesting about this zone is it's actually not law yet.

Kevin Marini:

[5:51] So a lot of people are paying attention to it because it's likely to become law soon. As of right now, they're trying to work on some of the language and figure out exactly what the zero to five area outside your home and other structures should look like. But one thing we know for sure is that, as you mentioned, embers are the driving force here. And what CAL FIRE says is 85% to 90% of homes that burn down, burn down from embers flying in. They catch things around the home on fire, which then leads to the house burning down. So this is super important because a lot of people I talk to think that a wall of flame is going to be coming at their house,  that actual huge flames are going to be burning down their house. Actually, it's these embers that are flying in. And let's be honest, they're little tiny pieces of burning material that sometimes fizzle out in the air, sometimes fizzle out in your lawn, but sometimes catch something on fire that burns your house down. So obviously, we got to pay attention to the zero to five feet clearance zone. I tell people, go home, take a measuring tape, put it out to five feet and walk around your home and your structures.

And it's not just your home, you may have a barn, you may have a shed. There's other structures as well to consider. And when you start doing that, you notice very quickly that you have some flammable stuff around your home that you probably should pay attention to. So, yes, I believe that's a great place to start.

Farmer Fred:

[7:28] Yeah. And it's not just plant material either. I have neighbors here in suburban purgatory who have seen their insurance rates go up because after an inspection, they were cited for piling up too much stuff, too much of their household goods or cardboard boxes against the side of the house.  And they had to clear them off immediately if they wanted to keep their insurance. 

Kevin Marini:

[7:53] Yeah. And I think that's often overlooked, right? Because people are paying attention to vegetation more so than anything when it could be that recycling bin full of cardboard or newspaper that catches the embers and starts the fire. I always point out things like outdoor furniture. You know, some of our outdoor furniture materials are extremely prone to ignition, right? Some of the cushioning, some of the material, the chairs and benches are made of. And also, I always think about this as a father. We used to have a play structure for our children right outside the house because you want it close by so you can look out the window and watch your kids. Well, a lot of those play structures are bone dry, right? So, I think you just bring home a very important point. That zero to five, that ember ignition zone is anything that's flammable, whether it's a plant, a piece of furniture, or cardboard or newspaper, believe it or not.

Farmer Fred:

[8:51] I know we're going to talk a lot about plants here, but think of the things you can't see that are flammable around your house. Like if you haven't cleaned out your gutters, it could be filled with tree debris that could start a fire. It could be poorly vented homes where the vents are too big and can allow those embers to fly into the attic for example. So there's a lot of checking on that you have to do on the house itself. But in the yard itself, That zero zone also means not even five feet of wood mulch on the ground.

Kevin Marini:

[9:23] Yeah, that's hard to take, especially for people like you and I who love mulch.

Farmer Fred:

[9:27] Well, we should say wooden mulch, like bark mulch. I would think five feet of gravel would be okay.

Kevin Marini:

[9:34] Well, yeah, I think if Cafire could write the book, they would love to see five feet of rock around every structure. But of course, that's not reality for a lot of folks. Now, we have to remember that we find ourselves in this situation because for 40, 50 years, the very foundation, pun intended, foundation of landscape design was to put foundation plantings all around our house, right? So, we have, in a sense, grown up here in the state of California with shrubbery all around our homes. And so, this isn't an easy fix for a lot of folks. A lot of people. I talked to a woman who had 60-year-old beautiful camellias all around her home that the insurance company was asking her to remove.

 So, in a lot of cases, there's emotional problems when it comes to getting rid of beautiful shrubs and trees, sometimes maybe with sentimental value, for example. But it's also the aesthetic appeal. It's hiding the area around your home, giving people privacy. I grew up with juniper shrubs all around my childhood home. We would pick those juniper berries and have wars in our neighborhood. And now I think back, I think that was the most fire hazard situation possible, right? Just the most flammable shrub that we pretty much know of, all around, surrounding a home. And so we find ourselves in a unique situation now where things that we used to value, such as those foundation plantings, now have to be rethought and potentially completely removed.

Farmer Fred:

[11:09] And especially the dead material that some plants can produce. And that's not just in that zero zone, the zero to five foot area, but in the next zone, which goes from five to 30 feet. There's a lot of plants that may look green on the outside, but inside they may be very dead.

Kevin Marini:

[11:25] Oh, yeah.  And this is one of the difficult things that I see all the time in our mainstream kind of landscape maintenance world. There is a lot of hedging and shearing of plants. And I don't mean like plants that you normally think of as hedges, like a boxwood hedge, right? Now that is kind of okay to hedge because they do pretty well in that situation. But in this day and age, a lot of landscape maintenance folks hedge and shear everything. And so you end up creating plants that aren't resilient to fire whatsoever. When you open them up beyond that little surface green area, you end up with dead material in the middle. I call them ‘ember catchers’. And I say that because if the plant was pruned naturally or allowed to grow to its natural form, it would not be an ember catcher, right? So this is a specific type of pruning that is leading to more of a fire hazard rather than fire safety. And so, yeah, I think looking at anything that is hedged and sheared on your property and really putting your hands in there and pulling it apart and peering in there and seeing what's going on in there will be really important for everybody to understand because as those embers come flying in, that's just the perfect spot for them to land.

Farmer Fred:

[12:50] Explain when people hear the term fire ladders, what does that refer to?

Kevin Marini:

[12:54] Fire ladders generally refer to vertical fire ladders, which is where you have, say, an herbaceous perennial underneath a medium-sized shrub, underneath a small tree, underneath a really large tree. And like I said, our landscape design for decades has been to layer plants and to get different textures and a different feel for our landscapes where you have these different sized plants and different colored foliage. That's been the plan. And now that's coming back to bite us because those ladders allow embers to catch fire that small plant  and that flame go quickly up into larger plants and eventually up into trees. When we get fire into trees, we have problems because that's where you get even more ember cast.

Kevin Marini:

[13:47] That's when embers are just spitting out of the top of those trees. Low fire close to the ground, believe it or not, Calfire kind of refers to that as good fire because it has a rejuvenating effect. And as long as it's not getting up into the canopies of trees, then we don't have a lot of ember cast going on. So the main fire ladder is that vertical path up into trees. However, there's another path that we have to be really aware of. And that is more of a horizontal path, a continuous line of vegetation. And so a lot of folks will,  on the sides of their driveways, for example, have a whole line of continuous vegetation stretching, you know, 50 yards, for example. Well, what happens is all it takes is those embers to get into one area and start a fire, and then it has a path all the way to your house or, again, to other vertical fire ladders. So it's not just those ladders that lead the fire up into trees. It's also the continuous vegetation without spacing in between that lead to that path of fire.

Farmer Fred:

[14:59] And gardeners, if there was one disease most gardeners have, it's ‘plant-itis’, where they must plant something. “I’ll find room for it. Don't worry”. And in five years or less, they have a jungle. And gardeners don't like to move because, heck, they've developed that property with so many plants. It's their haven. And they're living in a jungle. And that jungle, unfortunately, now, if it's in that five foot to 30 foot zone, is a fire trap.

Kevin Marini:

[15:28] Yeah. So the five foot to 30 foot zone, which, you know, the traditional defensible space zones are zone one, five to 30, and zone two, 30 to 100. And now, of course, we're going to have this zone zero, that's the zero to five. So the five to 30 is commonly called the lean, clean, and green zone. And so this is where things immediately get funny because here as I'm representing the Master Gardener Program, during the drought years, our messaging was what? It was remove those lawns, put in drought tolerant plants, use a ton of mulch, right? And now that messaging is basically the opposite. We've had to say, look, due to fire, having a little bit of irrigated turf around your home is a nice buffer for those embers coming in. So have a little bit. We now have many, many different types of sods and grasses that are more drought tolerant than the sods of the past. And so there's better options as far as drought tolerance or water efficiency, let's say.

Kevin Marini:

[16:37] But now we're saying, yeah, leave a little bit of lawn around your home for fire protection. And the mulch thing is very difficult because mulch has so many benefits. And we don't want to tell people not to use mulch. What we want to tell people is use it wisely, right? So depending on where you live, what fire zone you're in, and kind of what your defensible space situation is, you may be able to use a lot of it. You may only be able to use a little bit. But the one thing for sure is they have done study after study on the flammability of mulch. There's a great study out of the University of Nevada, Reno, that looked at all different types of organic mulches and their flammability. And what they do is they put these mulches down and they say, okay, how quick are these to ignite? If they ignite, how tall is the flame length?  If it has a huge flame length, how much radiant heat is it putting out, right? So, if a mulch is quick to ignite, has a huge flame length, puts out a ton of heat, guess what?

 That's the one you want to avoid, right? And so, if it's not so quick to ignite, and even if it has a small flame length or smolders and doesn't put out a lot of heat, then it's considered roughly fire-wise, okay? And so what they found was that the most widely used organic mulch in the state of California, which we know, and many people know, as gorilla hair,  which is shredded redwood and cedar.

It is the most flammable by far, by leaps and bounds. And so sometimes I feel like I can just look at that stuff and it would catch fire. On the other end of the spectrum, you have something called arborist wood chips or wood chips that come out of the back of tree trimming company trucks, right? The stuff that was usually a mix of green and brown material, it actually kind of starts to compost in there. There's usually a lot of moisture from the green material from the live tissues of the trees. And so that material they found is actually the most resistant to ignition, a tall flame length, and radiant heat. So if you're going to use organic mulches, use the arborist wood chips if you have access to them and it's doable for you aesthetically. I know a lot of people want mulch to look a certain way. We have a lot of options of kiln dried wood chips out there that you can buy in bulk, and they're all dyed, right? There's some that are dyed black. There's some that are dyed brown. There's some that are dyed kind of an orangey color. And so some people are choosing mulch just based on aesthetics. And I understand that. But if you're in a fire zone where you live next to one of these wildland-urban interface areas that you were talking about, the wildland-urban interfaces, I would recommend, if you're going to use organic mulch, to go with the arborist wood chips.

Farmer Fred:

[19:27] Yeah, and I would avoid that gorilla hair, which is the smallest form of wood chip mulch that you can get. It's very stringy looking. I remember when the new post office went in in Herald, California, and of course, I was assigned to help in the landscaping. And somebody made the mistake of buying gorilla hair mulch for this public area. And I think it was about two weeks later when they found a smoldering little fire going on in there because somebody tossed a cigarette in there.

Kevin Marini:

[19:57] There you go. Yeah. That's all it takes. That's all it takes.

Farmer Fred:

[20:00] Yeah. And basically that was the gorilla hair mulch that ignited. Definitely bigger wood chips are better than that. I noticed in that University of Nevada Reno study of the flammability of mulches. I would definitely not use shredded rubber or pine needles for mulch that has the highest rate of temperature, rate of spread and flame height.

Kevin Marini:

[20:20] Yeah. And then a lot of that rubber mulch is used around play structures, to kind of protect kids if they fall off the play structure. So not only is the play structure itself prone to being kind of dry and made of wood and being able to ignite, but you also have this mulch that's used a lot around them that is extremely flammable. And when it does get going, it burns very, very hot. And so, yeah, I think that we find ourselves in a situation where we have to really think through our use of mulch and use it a little bit more judiciously than maybe we did in the past where it was like, hey, get 15 yards and spread it everywhere, right? And the times have changed a little bit since then as far as our messaging goes.

Farmer Fred:

[21:06] I was surprised to see pine needles right behind shredded rubber as far as the danger of combustion goes. So, yeah, avoid pine needles and also shredded western red cedar.

Kevin Marini:

[21:18] Yeah. Now, the pine needle thing is interesting. So pine needles and oak leaves, you know, they get a bad rap as far as I'm concerned living up here in the foothills. A lot of people are always shocked to learn that I love pine needles and oak leaves as a compost constituent. But I don't want to start going down that road because I can talk composting for 10 hours. So, but pine needles, in nature, you have that top layer of kind of the fresh layer of dried out pine needles that is very easily ignitable. But if you actually walk through a mixed conifer forest area, what you find is there's a duff layer, and there is some pine needle material on top, but very quickly, it turns to kind of a duff that sometimes can really hold a lot of moisture for a long time. Now, by this time of year, in fall, it's all dried out. But it's pretty amazing how it does hold moisture pretty well for a good portion of the season. So what that study was doing was a lot of people will rake off pine needle mulch from around trees and then use it somewhere else. And so it's strictly just the real top layer of dried out pine needles. And that absolutely is to be avoided. I agree.

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DEFENSIBLE SPACE LANDSCAPING TIPS, PT. 2

Farmer Fred:

Let's get back to our conversation with University of California Cooperative Extension Defensible Space Consultant Kevin Marini. And we're talking about exactly how much space do you need between plants or between planted areas in order to defend your home from a wildfire. Let's go back and talk a little bit about spacing plants in that 5-foot to 30-foot zone. Obviously, it would be best to space the plants individually or in clusters and include hardscaping too, like walls or patios or pathways. How wide should a pathway be?

Kevin Marini:

[25:12] Good question. So a lot of times you see language such as ‘plant in the 5 to 30 zone in clusters, in islands’, like what you're talking about. And what's recommended is a three foot zone, at least. Of course, you can go farther out. But a three-foot buffer is a good rule of thumb between these clusters of plantings and other clusters of plantings. And within that three-foot area,  you want to use a completely safe material, something like rock mulch or DG (decomposed granite), for example. Or, like you said, hardscape, so flagstone or something like that.

 So that way, if embers fall into this little island of plants, which, again, you could be using mulch in that island, that is less likely to quickly spread to other areas. It's kind of a way to compartmentalize your landscape so that if embers come streaming in, it kind of burns just this area without spreading to the whole area. And so something as simple as a retaining wall can be the difference between your house burning down or not, right? Because a large retaining wall, three, four feet tall, could potentially intercept those embers coming in. Also, if you have landscape vegetation that's caught fire, it would meet up eventually against that retaining wall and be put out or burn out, hopefully. And so, yes, I think everything you said is correct. You're spacing out the plants both vertically and horizontally. You're planting plants in areas and leaving space between those areas. So not just between the plants, but between areas of planting. And then you're utilizing hardscape wherever you can to break up areas and kind of give yourself little mini fire breaks all over.

Farmer Fred:

[27:10] I'll have a link in today's show notes from this, the video that Cal Fire put out that they called a demonstration burn, where they built two little homes side by side, one with normal landscaping and normal hardscape; and the other very much hardened off to try to slow down the progress of aggressive burning embers. And the one thing I noticed about the house that burned down in 12 minutes versus the other one that never caught fire was,  besides the fact they had mulch piled up next to the house, they also had a wooden fence. And people forget that wooden fences can burn, which goes back to what you're talking about, rock walls and gravel walkways and things that don't catch fire.

Kevin Marini:

[27:55] Yeah. Yeah. So CALFIRE is the mandated entity to do official defensible space inspections. So no one else besides fire personnel do official defensible space inspections. Through UC, I do defensible space consultations and I do that on purpose. I use that word rather than inspection on purpose. And so that's an important resource for people, But, yeah, I think that they would love to see all wood fences that are close to homes or that lead to structures swapped out for, you know, ornamental iron. That would probably be ideal. But some sort of other fencing type that won't catch fire and lead the fire along the fence to a potential structure or another area that isn't hardened.

Farmer Fred:

[28:47] Yeah, this is great information if you're buying a new home somewhere in that wildland interface urban area and there's nothing there and you can get the hardscaping in first and then plant accordingly.

Kevin Marini:

[29:03] Yeah, yeah. And I think there's a lot of talk about using certain palettes of plants to create a fire resilient landscape. So, you know, traditionally,  these have been called fire wise plants. And the one thing that we know for sure is that every plant burns eventually. Right there's definitely a spectrum so you know if you have  a couple little succulents out in front of your house, they are are less likely to ignite and become a problem, as opposed to a mid-sized shrub, especially a juniper. So there's definitely a spectrum. But the idea that you swap out all of the plants in your landscape with quote “firewise plants” is really just a myth. I mean, that is not something that anyone in the fire world is recommending because it's not the species itself. It's how it's maintained and then how you organize your landscape that either gives it some resilience or makes it a hazard. I love how lavender is on almost every firewise plant list, right? When you go buy a one-gallon lavender at the nursery, Yeah, it's pretty firewise. It's nice and lush. There's no dead stuff in it. You can imagine embers being thrown at it and not igniting.

Kevin Marini:

[30:25] And so, yeah, sure, a one-gallon lavender, when you plant it, the first season is firewise. But we all know, well, maybe not “we all”, I guess I'm talking about gardeners know, that soon lavender grows and gets woody and starts accumulating dead stuff, right? And I've seen some plants that I would absolutely characterize as a fire hazard rather than a fire-wise plant. And so, again, that illustrates that this isn't about the species itself. It's about,  how is it going to be maintained? And is it going to be under something or near something where it leads to this path of fire?

Farmer Fred:

[31:05] We talked about clustering plants and spacing plants. And I would think that when you put in larger plants, the shrubs and the trees, I wouldn't go for the minimum space that they recommend. If they say a tree has a 30 foot spread, you would definitely want to plant the next tree over - if it's the same variety - more than 15 or 20 feet away. Because you want that space between the plants so that it isn't tree touching tree touching tree, then a tree touching a roof.

Kevin Marini:

[31:37] Yeah, that's a really great point. Because of course, people usually abide by the spacing that they see on the plant label, or they read it in the book, or they read online. And it may be different depending on where you live, and how your defensible space zones are organized and all of that stuff. And so you're totally right, there has to be additional thought or at least consideration. At this spacing, I'm going to have these branches touching each other eventually. And I need to have them farther apart than that. So the traditional spacing recommendations may not hold true for your landscape nowadays if you live in on