FIGHTING FIRE WITH FLORA : Create a Defensible Space Aroung Your Home by Clearing Brush, Thinning Vegetation and Exchanging Flammable Plants for Slow Burners.
Fire has always played a part in the California landscape. Chaparral not only survives periodic burns--it’s done so for half a million years--it benefits from them. Flames clean out dead and diseased plants and make room for fresh growth. And the ashes left improve the soil. The chaparral needs fire to stay healthy.
Unfortunately, fire does not distinguish between chaparral and homes. Once unleashed, it can consume both with devastating speed. The message was delivered with a vengeance in the firestorms that swept through Laguna Beach, Malibu and other parts of Southern California last fall.
And the upcoming dry fall months bring with them the likelihood of new fires.
Individuals can increase the odds that a home will be left standing when the smoke clears by creating a defensible space around it, says Capt. Dan Young of the Orange County Fire Department.
Especially vulnerable are houses near chaparral. Areas that border on or include chaparral encompass more of Orange County than you might think--places as urban as Cowan Heights and North Tustin, for example.
“When the Santa Anas occur and you’ve got 70-m.p.h. winds and the humidity drops to 7% and a fire breaks out, you can’t stop it,” Young says.
“Santa Ana-driven fires burn until they run out of fuel or run into the ocean--like the one in Laguna last year. Firefighters don’t put those fires out. We can’t.
“The best we can do is control the flanks and save individual homes.”
Two key factors that homeowners can control affect firefighters’ ability to save homes: space and time.
Firefighters need space in which to battle flames. If, for example, a home is so surrounded by dense vegetation that firefighters can’t get their equipment anywhere near it, it is indefensible.
Firefighters also need time. If, for example, a home is surrounded by landscaping that slows down a fire, they have extra minutes to arrive on the scene.
The best way to slow a fire is to deprive it of fuel. No plants are fireproof; even succulents will burn if the flames are hot enough. A better course is to reduce the total amount of plant material available to a fire.
“But that doesn’t mean creating a moonscape,” Young says.
“A buffer of healthy, well-watered, well-maintained, drought-resistant plants is better than bare ground. It actually improves the chances of your home surviving a fire.
“But dead vegetation is worse than nothing. It adds fuel to the flames.”
Creating a defensible space or firescape around your home can be reduced to a formula: Remove, reduce and replace.
Remove
Chaparral-fueled fires typically start when a spark ignites dry grass or litter, Young says. Therefore the most important thing you can do to prepare your landscape for the fire season is to eliminate both of these flashy fuels from your property now.
Cut tall grasses and weeds down to stubble within 100 feet of your house at minimum. “Throughout the entire property would be even better,” Young says. Also remove stacks of lumber or any other combustible litter.
Next, prune away all dead vegetation from trees and shrubs. Areas closest to the house--such as under the eaves--are the most critical.
Look beyond the surface, too, Young warns. “Junipers are often green on top but brown and dry underneath,” he says. “When fire touches them, they go up like torches.”
Coyote bush (Baccharis pilularis) is another example. While often listed as a fire-retardant plant, it can develop into a fuel-rich tangle of dry branches and leaves topped by a thin fringe of green if not routinely pruned to encourage new growth.
Finally, remove any vegetation that could act as a fire ladder, allowing flames to move from the ground to the crown of trees.
Scott Franklin, a fire management consultant and retired Los Angeles Fire Department officer, explains why:
“A pound of chaparral is equivalent to 8,500 BTUs--the same as a cup of gasoline,” he says. “Pour gasoline on the ground and ignite it and it just smolders. But aerate it--so that it’s all pumped up with oxygen--and it explodes.
“The same thing happens when ground fires move into the trees.”
Trees and tall shrubs provide fires with a lot of fuel, too.
“Keep the fire on the ground and you have two-foot flame lengths,” Franklin says. “Let it get into the trees, though, and you’re battling 80-foot ones.”
Most firescape literature recommends removing branches from the bottom six to eight feet from any tree over 15 feet tall. Remove any limbs that overhang buildings or are within 10 feet of a chimney as well. Also prune away the lower three or four feet of tall shrubs.
The idea is to create vertical space between ground-hugging plants and taller ones, which contain more combustible material.
Remove all pruned material from your property. Or, even better, suggests Franklin, chip it into quarter-inch pieces and use it as mulch underneath trees and shrubs.
“What you’re doing is rearranging burnable material--putting it on the ground where it does the least harm. And you’re preventing grasses and weeds from growing back and keeping the soil cool at the same time.
“Chipped biomass is the ultimate fuel break.”
Reduce
Next, create horizontal as well as vertical space between plants. The idea is to deprive an oncoming fire of a continuous fuel supply. Islands of shrubs separated by stretches of mulch, gravel or low-growing ground cover are preferable to solid masses of hedge, for example.
Trees should be well separated, too. And the steeper the slope, the greater the desirable degree of separation. That’s because fire moves faster uphill than down--hot air rises--and the steeper the slope, the swifter it climbs. Ten feet between the edge of one tree canopy and the next is often recommended for 0% to 20% slopes, and 20 feet for 20% to 40% slopes. A good rule of thumb for separating shrubs is at least five times the height of the shrub.
The 30 feet or so closest to the home should be planted the most sparsely. A stone or tile deck surrounded by succulents would be a far safer choice at the edge of a steep slope than a band of bushy foundation plants, for instance. On flatter parcels, an irrigated lawn would be a good choice.
The next 70 feet or so from the house should also be lightly planted. Many fire authorities recommend that plants in this band--which acts as a firebreak--be no more than 18 inches high. Natives are often a good choice, particularly on a slope, as their deep roots also provide soil stability.
If your property is larger, thin the next 50 feet or so of half its native vegetation, or plant widely-spaced trees and isolated islands of drought-tolerant shrubs. If your property is on a slope of 20% to 40%, create an additional 50 feet or more of defensible space by thinning the native vegetation by at least one-third. However be careful not to take out too many deep-rooted shrubs, especially on a slope, to prevent soil erosion and slope failure.
California sagebrush (Artemisia californica) , black sage (Salvia mellifera) and buckwheat (Eriogonum fasciculatum) are good candidates for thinning as they are more fire-prone than other natives.
Remove deadwood and fire ladders from the remaining vegetation. Michael Lindsey, a Laguna Beach landscape architect and native plant specialist, also thins out the interiors of large specimens.
“I prune shrubs into more tree-like shapes,” he says. “It not only reduces total fuel load and the likelihood of shrubs acting as fire ladders, but I like the sculptural look it creates, too.”
Replace
Pyrophtes are plants that are high in oils and resins, making them extremely flammable. They can be disastrous landscaping choices in areas that interact with the chaparral.
“If you wanted to design 200 pounds of wood to burn as quickly as possible, you’d design a Christmas tree,” Dan Young says. “Even when healthy, pines are a fire hazard.”
If you retain these trees, keep them well-trimmed and with at least 10 feet of clear space between any building or other plant.
But replacing them with more fire-resistant species, such as native oaks or sycamores, would be a safer option.
Palm trees with a buildup of dead fronds beneath their crowns are highly flammable, too. Other common pyrophtes are cedar, cypress, juniper, spruce, bougainvillea and pampas grass.
If you have these species on your property, consider replacing them with plants with higher fire resistance.
Keep in mind that no single firescaping plan is suitable for every home. Each site has its own profile and problem areas. There can sometimes seem to be inconsistencies in expert recommendations, but differences are often the result of suggestions developed for different scenarios. Each situation needs to be evaluated individually.
Final Caveat
If this sounds like too much work, consider this picture:
“Walk around your house and imagine what would happen if the sky were raining sparks--because that’s what happens in a firestorm,” Young says. “Think about those sparks dropping from the sky and ask yourself what they would ignite first.
“That’s what you want to get rid of.”
More Firescape Information
* The Wildland Management/Hazard Reduction Section of the Orange County Fire Department has literature and specific questions and answers about firescaping your property. (714) 744-0500.
* “Firescape: Landscaping to Reduce Fire Hazard”--a brochure of the East Bay Municipal Utility District. Send 50 cents to cover costs to the District, P.O. Box 24055, Oakland, CA 94623.
* “California Wildfire Landscaping,’ by Maureen Gilmer, a handbook on dealing with wildfires--before, during and after--including creating bands of protection with plants. Paperback, Taylor Publishing, $10.95.
* “Fire Safe--Inside & Out”--a brochure published by the California Department of Forestry. Write CDF Southern Region, 2524 Mulberry St., Riverside, CA 92501. Free
* Firescape Demonstration Garden--Fire Station No. 7, 2411 Stanwood Drive, Santa Barbara, Calif.
