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Fire Prevention

Creating a Defensible Garden


Fire season is officially open. Fire is natural in the foothills of Southern California; many of the plants that have been growing here for the last few thousand years need fire to release their seeds from dormancy. Fire also facilitates cycling of essential nutrients as the ash formed is deposited on the soil surface. Clearing out the dense cover also allows light into formerly dark areas so that dormant seeds may sprout.

Many shrubby species will soon resprout from underground stems, and it won’t take many years to have a dense thicket again: a source of fuel that is just ripe for the next spark and puff of wind to create an inferno. These native plants are uniquely adapted to such catastrophic events by having an enlarged underground burl that can quickly form new shoots using stored nutrients. Their deep roots are able to survive the intense temperatures that occur during a fire (even one and a half inches below the surface, the soil may reach 300 degrees Fahrenheit). These stalwarts of the chaparral will, within just a few years, dominate the scenery once again. The proclivity for this fiery renewal of the native chaparral and the human desire to occupy available space creates a recipe for disaster. As houses are built deeper and deeper into the native vegetation, it is only a matter of time until wildfire strikes near enough to pose a serious threat.

Fire will travel wherever there is something to burn. Designing a garden in the wildland/urban interface means choosing plants that don’t result in thickets of secondary, woody growth. Softer perennials and especially those that don’t have aromatic foliage (a clue that they are full of flammable oils and resins) are obvious choices. Isolate groups of plants in “islands” surrounded by “seas” of groundcovers so that they don’t create “ladders” for the fire to follow.

Other rules to remember are more or less common sense. Trim overhanging branches and keep them at least 15 feet away from roadways. Rake up dead leaves, barks, and twigs, and remove them from roofs and gutters. Be sure to keep palms that hold their old fronds trimmed up, as well. Don’t locate the firewood pile near any structures, and keep vegetation mowed low around it. Trim vegetation while it is still somewhat green, and beware of stones hiding in the grasses that in collision with mower or tractor blade can cause sparks. It’s not a bad idea to have a hose ready nearby to dampen things down and, heaven forbid, get the upper hand quickly should these precautions fail. One last caution: Make sure mowers, string-trimmers, and chainsaws are in good condition to avoid electrical shorts and gas leaks that can fuel the tiniest spark.

If choosing plants that are attractive and less likely to burn seems a daunting task, there is one great place to go for inspiration. Visit the Firescape Demonstration Garden on the corner of Mission Ridge Road and Stanwood Drive right across the street from the firehouse. Everything from groundcovers to flowering perennials are planted here, and trees and shrubs are trimmed to the recommended guidelines. Remember, 95 percent of all wildfires are caused by people. A little caution and advance preparation can increase the odds for a defensible garden that may even provide a measure of protection against wildfire.

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