Landscaping may be the single greatest determinant of fire vulnerability.
With the right landscape design, plant species, and site up-keep, you can effectively buffer your home from wildfire and the airborne embers that often start home fires. The most important overarching principles to keep in mind are:
(1) create a defensible space—extending at least 30 feet from your building footprint—that is primarily non-combustible and can be managed easily; and
(2) bolster the natural ecosystem to remedy site-specific wildfire vulnerabilities like wind and dry soil.
See our California Native page for a list of all plants native to the Los Angeles area, some of which can be used in wildfire-resilient landscaping.
Content:
Landscape Design
36. Study site characteristics to understand vulnerabilities.
Before developing your site landscape, understand the key vulnerabilities that you’ll be dealing with. It may be that the surrounding topography channels wind like a funnel across your site; or that being at the bottom of a hill makes your site particularly susceptible to debris flows that often occur after a fire. In each case, landscape design can help to lessen the vulnerabilities, but you must first identify them.
ACTION
» Start by making observations on your own; note common wind direction and severity, rain flow and runoff pattern, and potential debris flow vulnerability. You might then consult with a local landscape expert to confirm observed vulnerabilities and determine how best to address them.
37. Design a combustible material-free zone from 0-5 ft of the building footprint.
A key to fire resilient landscaping is to have a barrier of at least five feet in which all materials used are 100% inert to fire. A completely combustible free zone between 0-5 ft of a building footprint is expected to make its way into building codes in the coming years.
ACTION
» Install landscape fabric underneath the buffer to prevent weeds from compromising the boundary. Use rock, concrete, or tile as the surface material. If you use part of this space as a patio, ensure all furniture and decoration are non-combustible. For fences that abut an exterior wall, use metal or concrete for the portion that is within this defensible space.
RESOURCES
38. Create a defensible space from 5-30 feet of building footprint with sparsely planted small herbaceous plants that are high in moisture content.
Fire moves both horizontally and vertically. For this defensible zone, consider a plant’s relationship to other plants as well as its proximity to vulnerable building elements. All plants burn, but not at the same rate. Native species adapted to fire and non-invasive succulents are preferred to reduce the risk of fire.
ACTION
» Space plantings so their crowns don’t touch. Take care to prevent fire-ladders by ensuring adequate space between low-lying plants and low-branches of the trees or large shrubs above them. Importantly, plantings within this zone should also be spaced far from vent openings or windows. Ensure plants in this zone remain well hydrated either with an automatic irrigation system or by periodically watering manually.
RESOURCES
39. Design outermost landscaping to break up prevailing wind, defend against debris- flows and catch embers.
Beyond your defensible space, work with the native landscape to enhance site resilience. Once you’ve analyzed your site’s vulnerabilities and exposure (see recommendation #36), use new plantings, retaining walls, and other site features to defend against wildfires and debris flows.
ACTION
» Plant trees in the way of prevailing winds to catch embers and slow down wind speeds. Tree groupings (with proper separation between canopy branches) can also help keep winds and airborne embers well above the top of a home. California Live Oak is particularly effective at breaking up winds and catching embers. There are programs to reforest California in native Oak, so you may be able to obtain inexpensive or free saplings. See recommendation #44–45 for periodic maintenance suggestions.
» Use rock walls and large tree groupings to create a blockade between the house and the anticipated debris flow path. These features should be designed at an angle to the debris flow path to channel debris flows away from the home.
RESOURCES
40. Design hardscape features like driveways, walkways, and patios to create firebreaks throughout the yard.
Firebreaks are gaps in vegetation or combustible materials on the ground, which stop or slow fire progression. Bare dirt firebreaks can have adverse effects if they aren’t properly maintained. Hardscaped firebreaks, or those made with concrete, stone or tile, can be a more effective deterrent and serve an aesthetic or functional purpose.
When designing handscape features like driveways or walkways, consider whether they might be easily redesigned to more effectively block fire from moving toward your home. Always design firebreaks along hill contours, not up the hill. Uphill firebreaks aren’t as effective at stopping the naturally uphill movement of fire and bare dirt uphill firebreaks can create landslides.
RESOURCES
41. Use planting schemes and topographical adjustments to improve the soil’s water retention.
Wildfires are fueled by dry, dead plant debris that result from drought conditions. A landscape that better retains and stores water can improve resilience against drought and decrease the dry plant fuel on your site. Water retention is a function of soil characteristics, plants, and topography.
ACTION
» Choose plants with deep root systems to pull water from deep underground toward the surface. Use Rock walls or berms on steep slopes to slow water runoff which increases the amount absorbed on site. Consult with a landscape designer for site-specific options for improving water retention.
Plant & Material Selection
42. Use only native plant species designated as fire-resilient.
The plants you choose to surround your home with will partially determine how well you can buffer wildfires. One of the most important considerations is whether your plants are native to this region of California. Native plant species have evolved to manage the severity of wildfires, so they likely won’t burn as easily, and when they do burn, their burn characteristics may be more favorable than many exotic invasive species.
ACTION
» Before adding any new vegetation, review local plant species lists (see resources #1,#2 & #3) for guidance. You can also contact local nurseries or landscape contractors for advice specific to your site characteristics. Remember that all plants burn. While plants that are recommended online or by professionals are a good start, it’s important to still follow best practices with regard to landscape design, plant spacing, and maintenance guidelines regardless of the plants used.
» Review lists of highly flammable plants (resource #4) to avoid and remove them if they are already onsite. Examples include ornamental juniper, Leyland cypress, Italian cypress, rosemary, arborvitae, eucalyptus, and some ornamental grasses.
RESOURCES
California Native (all native species, non-fire specific)
43. Do NOT use railroad ties anywhere on site.
Old railroad ties are commonly used for aesthetic or functional purposes in a landscape. However, the wood is treated with creosote as a preservative, which is toxic and highly flammable.
ACTION
» Do not use railroad ties on site, and dispose of existing railroad ties. Follow proper disposal protocol as designated by your local solid waste disposal service.
Site Maintenance
44. Maintain vegetation by clearing dead plant debris, cutting tree branches and thinning undergrowth.
No matter which plants are chosen, your site will need to be maintained at least once a year.
ACTION
» Remove lower limbs of trees within 30 feet of the house. Thin trees within 100 feet of house to avoid connected canopies and remove brush and debris from under trees. Clear dead plant debris, especially along walls, beneath decks, gutters, and ridge vents.
RESOURCES
45. Apply Phos-Chek fire retardant to surrounding vegetation and wood surfaces at the start of the fire season.
Phos-Chek® is a long-term fire retardant effective on all cellulose fuel (e.g. vegetation and wood surfaces). Phos-Chek is comprised of phosphate salt, which is environmentally safe (in small doses), and qualified by the USDA Forest Service and included on the USFS Qualified Products List. This is the compound used by the US Forest Service when treating wildfires via airdrop. When in contact with flame, the surface of the treated material turns into non-flammable carbon and water, starving the flame of fuel needed to remain burning. This type of retardant is very different from the foams and gels applied to a home’s envelope during active fires which only remain effective for several hours.
ACTION
» Mix the phosphate salt powder with water in the prescribed ratios. Apply Phos-Chek, with a common garden sprayer or other spray equipment. Spray on nearby vegetation in a pattern that creates unbroken firebreaks around your home. Also spray underneath trees or large shrubs to prevent fire-ladders. Phos-Chek is effective until it is washed away by water (e.g. rain or sprinklers), at which point it will need to be reapplied.