Fire-Safe Landscape Design
Co-written with Fire Safe Marin
From Colorado to California, wildfires are intensifying at an alarming rate.
California’s recent McKinney fire is just the latest example of the more expansive and severe blazes that have become terrifyingly common throughout the West.
For homeowners, fire safety is rightly on the mind.
To Burn, or Not To Burn
Good news! Firescaping – designing yards to resist fire – can protect our homes and neighborhoods by slowing the spread of fire.
But there’s a twist: several tried-and-true landscape design practices turn out to pose significant risks for fire safety.
If we are serious about protecting ourselves and our neighbors from fire, we need to reconsider some of our landscape design preferences, cutting out old practices that don’t account for today’s elevated risks, and welcoming new approaches that get us the style and function we want while improving our safety.
Below, we’ll walk through the fundamentals of fire-wise landscape design: how fires are transmitted, the biggest fire risks posed by landscape design, and best practices for improving fire safety. We’ll also share some tips for achieving your personal design style while still prioritizing fire protection.
Let’s get into it!
How Fires Spread in a Yard
There are three fundamental ways fire spreads across a property:
Embers are tiny bits of ignited wood or debris borne on the wind ahead of a wildfire. When embers land on flammable material, they can ignite a new fire.
Embers can travel for miles ahead of an active wildfire, and are responsible for 90% of home ignitions.
Fire ladders (also called fuel ladders) happen when ground-level plants beneath a tree canopy catch fire. As the flames rise from below, they can spread to the tree crown, where strong winds and wide-spreading branches disperse flames and embers over large distances.
Because of their height, roofs are particularly vulnerable to flames and embers emanating from tree canopies.
Following the fuel
Fires spread in the direction of available fuel. In a landscape, this means plants and hardscape materials that are easily combustible create the path by which fire will most readily travel. The goal of fire-wise landscaping is to stop these three methods of fire transmission.
Writ large, fire-wise landscape design seeks to interrupt each of these modes of transmission.
Fire Risks of Traditional Landscape Design
A handful of common landscape design practices make it easier for fire to spread through yards and, ultimately, to burn houses and other structures.
In terms of damage to homes, the greatest fire risk comes from landscape features within the first 5’ of a building – what fire experts call “Zone 0”.
Planting beds along the base of exterior walls are a staple of landscape designs across a range of styles – you see foundation planting everywhere.
Unfortunately, foundation planting essentially stockpiles fuel next to homes. When foundation planting features fire-prone plants like dense shrubs or woody perennials, the risk of the structure igniting only increases.
Trees and large shrubs near the house
When tree branches touch or lean close to a structure, they can easily transmit flames and embers. They also drop their leaves on rooftops and in rain gutters, making houses more likely to ignite.
Some popular species are particularly combustible. Juniper, Italian Cypress, Arborvitae, Bamboo, and some (but not all!) ornamental grasses burn easily.
Such species are routinely used along fence lines and adjacent to buildings – we’ve all seen massive juniper expanses spreading across front yards, cypresses and arborvitaes accenting corners and entryways, and bamboo screens lining the length of side yards. While commonplace, such practices are not unlike piling kindling up against the house.
- Hedges and privacy screens. Some fire-prone species are commonly used as hedges or tall privacy plantings, typically situated along the boundary of a property, or as a foundation planting. When ignited, these features quickly transmit fire along their length.
- Bark mulch. Mulch is excellent for suppressing weeds, regulating soil temperature, and preserving soil moisture. Mulches made from organic materials, like bark mulch, also help to build soil health as they break down. Even better: bark mulch is cheap! The downside? Bark mulch is a fire hazard, especially the shredded “gorilla hair’“ stuff. There is a place for certain types of bark mulch in a fire-wise landscape, but the traditional route of using mulch to blanket beds along houses, decks, and other landscape features puts those structures at greater risk of catching fire.
- Planting under windows and air intakes. Planting beneath or near sliding glass doors, chimneys, vents, and windows increases the risk of fire entering a home.
- Planting on or under structures. Vines attached to walls, planting beneath elevated decks, tall plants under eaves, and similar situations where vegetation is positioned to ignite structures all increase the likelihood of igniting structures.
While there are many more fire safety measures to consider across an entire property, these Zone 0 factors pose the greatest risk to homes, and should be the first thing a fire-wise landscape addresses.
No Plant is Fireproof
Eventually, any plant will burn. That being said, some plant species burn easily, and others do not.
Certain plant characteristics influence fire-resistance:
- Plants high in moisture are less likely to ignite (this is why succulents, which store moisture within their leaves, are good at resisting fire). The opposite also holds true: plants with dried-out leaves and branches burn easily. Drought-tolerant plants aren’t necessarily fire-resistant, but they can avoid drying out better than species with higher water requirements.
- Plants with lots of wax, oil, or resin content burn more readily. Many conifers fall into this category.
- Plants with a dense structure are more likely to burn than a plant with an open structure, particularly if dead plant matter like leaf litter or branches accumulates within the foliage.
- Plants that shed lots of leaves, needles, dead branches, bark, and other litter accumulate fuel at their bases, making them more likely to burn.
- Plants with fuzzy, stiff, small, or fine, lacey leaves all tend to burn more easily. Evergreens with needles or blade-leaves are quick to burn as well.
These tips will help you intuit whether a particular species will resist burning, but it’s always best to consult a reliable resource like a local nursery or fire-safety organization to confirm a plant’s fire-resistance before putting plants in the ground.
Including native plants in a design is a great way to reduce maintenance requirements; having evolved to thrive in local conditions, natives tend to require less maintenance than introduced species (they also offer exponentially more habitat value).
Tip: Homeowners in the greater Bay Area looking to select fire-resistant species can take advantage of Fire Safe Marin’s excellent list of Fire-Smart Plants.
Cal Fire and Cal Poly University also provide fire safety information (and a lot of other great tree information) on their excellent SelecTree website.
Species selection and design choices are crucial to fire safety, but how a landscape is maintained is often even more critical.
How does maintenance affect fire safety?
- By clearing away dead leaves and pine needles, woody debris, diseased or dried out plants, and any other dead material, maintenance eliminates combustible fuel. No fuel, no fire.
- Keeping plants well-irrigated avoids them drying out, in turn helping them to more effectively resist burning. Even the most fire-resistant plant can become fuel if not maintained in a healthy condition.
- Cutting back herbaceous species like lavender and sage prevents them from developing woody stems, reducing their likelihood of burning. It also keeps them looking soft and fluffy!
- Pruning trees and large shrubs to remain safely distanced from structures reduces the risk of flame transmission.
Tip: keep branches at least 10’ from any structures, including chimneys and stovepipes.
- Regularly clearing out debris from rain gutters and areas under decks and other structures means lower likelihood of those features catching fire.
The impact of maintenance on fire safety puts a lot of responsibility on homeowners, but designers can help to alleviate their burden by developing low maintenance designs.
Fire-Resistant Landscaping Fundamentals
Now, let’s talk design!
Remember Zone 0? That’s the area between 0’ and 5’ of a house or structure.
We already listed things not to do in Zone 0, but here’s what you can do in that space to develop a fire-wise design:
This is a key concept of firescaping. When cleared of flammable vegetation and combustible materials, Zone 0 acts like a fire-resistant buffer. Maintaining defensible space is highly effective at protecting homes from fire, and should be a homeowner’s top firescaping priority.
What’s allowed in Zone 0?
- Use inorganic mulches like gravel or decorative stone, and avoid organic mulches like bark mulch.
- It’s best to keep planting minimal (experts advise skipping planting almost entirely), relying instead on hardscape features like paving or stone.
- Some planting is fine, though all planting should be fire-resistant. Succulents are an excellent option, as are low-growing perennials. In general, plants in zone 0 should be short – save the taller species for areas further from the house.
- Use plants in areas where they will have the greatest visual impact. Growing plants in containers is a good strategy for elevating their visual impact while also reducing their risk of catching fire.
After Zone 0, between 5’-30’ of the home, comes Zone 1.
- Plants can get a little taller in Zone 1, but should still stay relatively low (the further from the house, the taller plants can be).
With denser planting comes an increased emphasis on maintenance—make sure plants in Zone 1 are healthy, well-hydrated, and clear of debris.
Prioritize non-woody species like pollinator-friendly perennials, though it’s fine to incorporate a small amount of well-maintained shrubs, or even a few small trees if they’re kept free of dead plant material (opt for fire-resistant, broad-leaved species).
Finally comes Zone 2, extending from 30’-100’ from the house.
- Planting areas can get larger in Zone 2, and greater quantities of shrubs can be used.
When Zone 2 features mature canopy trees, it can also incorporate “shaded fuel breaks”. Trees’ canopies provide shade that can actually lower fire’s intensity. The trick is to limb up the branches and clear highly flammable fuel from below the trees. Plant low growing (ideally native) groundcover species beneath to keep flames from moving up the trees.
If you have any wood piles or propane tanks, it’s best to keep them in Zone 2 as well.
Some firescaping principles can be applied to the entire yard.
Plant in islands + use hardscape breaks
Once a fire ignites, it can quickly consume an entire planted area. Limiting the size of planting areas – planting in “islands”- limits the area through which a fire can rapidly spread.
You can limit the size of planting areas by introducing hardscape breaks. Walkways, patios, rock beds, and retaining walls all block the advance of fire along the ground so long as they are constructed from nonflammable materials. Even a low patch of well-irrigated groundcover planting can be an effective firebreak.
Planting in smaller zones is particularly important in Zones 0 and 1. Planting areas can get larger in Zone 2.
Even with firebreaks on the ground, fire can still spread by embers. It’s best to keep walkways and other firebreaks at least 4’ wide to discourage embers from jumping to adjacent planting areas.
To avoid creating a fire ladder, limb up trees so that there are no branches within 6’ of the ground.
When there is planting beneath a tree, leave a gap between the top of the planting and the lowest branches that is at least three times the height of the ground level planting.
Much as with densely-structured plants, fire is more likely to spread through densely-planted areas. Designs that allocate a bit of breathing room between plants are less vulnerable to the spread of fire.
Dense planting designs are generally of higher habitat value. Incorporating patches of fire-resistant, native groundcover planting between taller plants can be a way to hang on to planting density without sacrificing ecological value.
Avoid dense evergreen hedges entirely, particularly hedges of fire-prone species.
You can hang on to mulch and its many benefits by using it in a fire-wise way.
In Zone 0, stick to inorganic mulches like gravel. Don’t use any organic mulches in Zone 0.
In Zone 1, you have two organic mulch options: compost or composted wood chips (both of these resist fire better than other bark mulches). Inorganic mulches are also fair game in Zone 1.
As with planting, use hardscape breaks to separate mulched areas.
In Zone 2, zones of compost or composted wood chips can be used to separate larger planting areas.
In any zone avoid bark mulches made with small or shredded particles.
As a living alternative to mulch, try planting patches of fire-resistant groundcovers like Sedum between scenes of ornamental plants.
Fire burns faster and more intensely up slopes, especially steep ones. The steeper the slope, the further apart shrubs and trees need to be to avoid them transmitting fire uphill.
On flat land, trees should have 10’ between the edges of their canopies, and shrubs should be spaced at a width equal to twice their height. Those ratios double on slopes above 20%, and triple on steep slopes above 40%.
It should go without saying, but to reiterate, all of the above firescaping practices must also involve regular maintenance, prioritizing fire-resistant species, and avoiding fire-prone species.
Firescaping in Your Own Style
Many factors weigh into decisions about fire safety: the level of fire risk to your house/region, your style and functional goals for your landscape project, the level of habitat value you hope to provide, your personal tolerance for risk.
Just because a homeowner wants to be safe from fire, they shouldn’t be forced into a landscape that doesn’t achieve their goals.
Fortunately, fire-wise design is not an all-or-nothing proposition. On the contrary, fire safety can be approached as a gradient. Designers and homeowners should begin a project with an open discussion about fire safety to determine how high a priority it is, and how thoroughly the homeowner wishes to implement fire safety practices across their property.
If you ask us, everyone who lives in an area prone to wildfire should at a minimum create a defensible in Zone 0. We also advise doing what you can to make Zone 1 as fire-wise as possible.
How can you do this and still achieve your desired function and style? Glad you asked!
Much of planting style is expressed not through species but through the way plants are physically arranged.
Homeowners seeking a formal design can arrange plants in straight rows or geometric blocks, while still allocating enough space between plants to avoid rapid transmission of fire through a planting area.
Homeowners seeking a wilder, more informal feel can arrange plants in scenes, clustering small masses of a few species together to create a focal moment, then allocating some breathing room around the edges.
Craving a dense planting design? Don’t despair. Use patches of well-irrigated, ideally native groundcover planting to fill gaps between larger ornamentals. This will get you the look of a dense planting design without the elevated fire risk. It will also cut back on your spending at the nursery.
Beyond being excellent fuel breaks, hardscape features like paths and walls also happen to be excellent frames for planting. The materials and form of a hardscape feature along the edge of a planting area plays a crucial role in expressing an overall design style.
Long, gracefully curving edges made from rustic pavers lends a welcoming, traditional feel.
Straight lines and sharp corners from features like concrete walls, corten steel edging, or oversized pavers interspersed with decorative stone express a modern feel. This approach looks particularly attractive when framing billowy grasses, rangy perennials, and sculptural shrubs like larger Manzanitas.
Focus on using framing to achieve your aesthetic and functional goals, and the hardscape breaks will be baked in.
Functional areas like fire pits, gathering spaces, or dining zones all double as defensible space.
Functional areas are fair game for all sides of the house, front yard included. This is a win for fire safety, and for helping you maximize the utility of your outdoor spaces.
Determine the optimal location for each outdoor function you hope to include in your landscape design—kitchen and dining here, seating there, play area over there. Follow this by plugging in paths for convenient and pleasant circulation between each functional zone. Finally, plug in your planting islands in the spaces that remain.
Follow this formula, and it’s easy to end up with a fire-wise Zone 1, replete with attractive planting islands and hardscape breaks. The best part? You’ll have gotten there by focusing on your goals, not on fire—the safety is a happy byproduct of the design process.
Tip: keeping functional areas near the home helps to fill up zone 1 with noncombustible areas. It also keeps your functional areas conveniently close to the house, and to each other.
Whatever your style, whatever you hope to do with your outdoor spaces, focus on those goals when you approach a design. Once you’ve identified those goals, work firescaping into your implementation. With good communication and an open mind to new outcomes, you can get the best of both worlds—design satisfaction and fire safety.
Get Started With Your Fire-Safe Landscape Design by Yardzen
Yardzen’s award-winning online landscape design is tailored to clients in all fifty states in the US.
Our design process begins with understanding your space, your aesthetic preferences, and a discussion of your budget and vision to minimize surprises when it comes time to build. Homeowners who live in areas that are prone to wildfire can also request that their yard design use firescaping principles to reduce the likelihood of home damage if their area is affected by fire.
Our top-notch designers then develop a personalized vision for your yard, shared through 3D renderings, 2D plan drawings, and plant and material lists. Your design will capture the look, feel, and function you are hoping for, all while keeping costs within range.
Once your design is complete, we’ll help you connect with a local contractor from our Pro Network of vetted professional landscapers to install your new design.
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