Your Landscape is Your Home’s Best Friend in a Wildfire
By Ron Hodgson PhD
The landscape surrounding your home provides many hours of enjoyment and is a place of beauty and comfort. It provides an aesthetic setting for your home and a personal environment for family leisure, learning, and togetherness.
At the same time, the landscape provides an important defense for your home in a wildfire. It keeps flames away from the buildings. It provides a safer area for firefighters to work to stop flame spread and attack any fires that start on the building from embers and firebrands.
Homes surrounded by well-designed and maintained landscapes are far more likely to survive wildfires with little damage. Here are some ways to reinforce your landscape’s ability to protect your home.
You want a landscape that burns with a low intensity. You want flames to spread slowly and stop all together at firelines you build into the landscape. And, you want to keep the fire on the ground and out of the treetops.
Slow it down. Fire spreads quickly through fine, loosely packed fuels such as standing dry grass. It spreads more slowly through coarser and more compact fuels such as larger downed tree limbs and logs. Mowing grass reduces the fire’s rate of spread.
Thinning brush and breaking up continuous vegetation into patches and groups separated by open ground slows fire spread. Building firelines into the landscape can stop fire spread. Firelines can be strips of bare earth, gravel or paved driveways and paths, retaining walls, and well-irrigated lawns or planters with high water and low oil content plants such as begonias and succulents. Fire retardants can also be applied to dry, flammable vegetation to slow down fire spread or stop it all together.
Cool it down. Reducing the amount of fuel available to the fire cools it down. Do these things: Thin and remove brush and trees to create a more open, park-like landscape. Break up continuous vegetation into well separated clumps and patches. Remove dead branches from brush and trees and clean up leaves and downed wood. Move wood piles, construction materials, and other flammables far away from the house. Shield them from ignition by embers. Clear around and under propane tanks.
The two yards from the foundation outward should be free from anything that will catch fire and burn. Keep fire well away from buildings and other values-at-risk. The fire-free zone around a house can be designed as an attractive, useable hardscape containing only high water-content plantings and ignition resistant construction materials. Retardants can be applied annually to flammable vegetation, fences, and other wooden structures to reduce the chance of ignition and slow fire spread.
Keep it on the ground. Dead leaves and twigs can spread fire under brush. This can ignite dead twigs and pine needles draped in the limbs. Burning brush can ignite the lower branches of trees. The fire then spreads upward through the branches to ignite the tree crown. This arrangement of fuels is known as a fuel ladder. It can quickly convert a slowly spreading, relatively cool surface fire into torching trees.
Under the right conditions, fire in one treetop can spread to another and then to another in a crown fire. Torching trees and crown fires generate many embers and fire brands that quickly spread the fire across fuel breaks and fire lines. Embers and firebrands are the principal cause of structure ignitions in wildfires. Crown fires are difficult to stop and dangerous to fight. Fire brands falling ahead of the fire cause the fire to leapfrog across unburned landscapes starting new fires. Such fires spread fast and burn very hot.
Landscaping to keep fire on the ground and separating small clusters of trees so that fire cannot easily spread from one treetop to another is essential to protect homes, neighborhoods and the people who live in them.
Fire wise landscaping uses knowledge of fire behavior, ornamental and native plants, fire retardants, ignition resistant construction materials, and the talents of skilled landscape architects, designers, and contractors to create and maintain safe homes and neighborhoods. This makes it possible to live safely with wildland fire in high fire hazard environments.
S.A.F.E Landscapes: Southern California Guidebook to Sustainable Fire Safe Landscapes in the Wildland Urban Interface. https://ucanr.edu/sites/SAFELandscapes/files/79452.pdf
Fire in California – Preparing Your Landscape. https//ucanr.edu/sites/fire/Prepare/Landscaping
Defensible Space: Home Builder’s Guide to Construction in Wildfire Zones – FEMA. https://www.fema.gov/media-library-data/20130726-1652-20490-9209/fema_p_737_fs_4.pdf