The Santa Ana wind, which hits Southern California like a parched hurricane almost every fall, followed an unusually dry winter and spring this year. The California summer was, as usual, hot and rainless. An autumn with dry earth, dry trees, dry grass—all it took was a spark.
The sour though sensible aftereffect of the Malibu and San Diego County fires is that California homeowners are beginning to look at their trees and plants not as beloved and beautiful green stuff but as fuel for a future fire.
The lingering edginess and increased sensitivity to this threat is a lot like the way Californians feel about earthquakes. It would be nice to put the wineglasses up there on a shelf over the sink, but in a quake those glasses would be dangerous missiles. Similarly, it would be lovely to have that oak tree at the corner of the house shading the deck, but fire could race up the tree trunk to the roof. Now, in fact, wooden decks are strongly discouraged, and should be replaced by stone or cement patios. A rose-covered cottage is now perceived as a firetrap.
When your biggest investment is a house in fire country, every green thing that could turn brown starts to look like "flammable material," in the terminology of firefighters. Indeed, a relatively new law requires Californians to remove dead, brown flammable material and to severely thin out even potentially flammable green material. Property owners must maintain a lean, clean relatively bare zone in an area of 30 feet immediately surrounding a house, plus a "reduced fuel zone" in the remaining 70 feet or to the property line.
It's quite a precedent. On the positive side, the clear space makes the house less likely to ignite, though in a high wind all bets are off. The bare area makes defending a home less dangerous for firefighters. But this cleanup also means no more picturesque tall grasses; no more woody trumpet vine or wisteria winding up the front porch pillar; no more paths carpeted with pine needles or wood chips; no groves or tall hedges, since under the law, trees must be at least 10 feet apart, 30 feet apart on a slope.
Home gardeners are advised to space shrubs as well as trees far apart to prevent fire from jumping from bush to bush. A disconcerting passage on this topic from one University of California advisory (PDF) reads, "The actual between-plant spacing depends on one's aversion to the risk of fire spreading to one's home, and the associated chance of losing it." We presume that all those property owners not averse to collecting insurance (and not worrying about losing the photo albums, CD collection, and the family cat) can go ahead and put their azaleas in close formation.
The California Department of Forestry and Fire Protection Web site features a folk song—no kidding—about cleaning up your yard, and a scary movie ("Without 100 feet of defensible space, this house never had a chance.")
Some Southern Californians, eager to protect their real estate, have already complied with excessive enthusiasm, clearing their plots down to bare earth. This produces not only a very dreary yard but also a yard vulnerable to erosion, exposing the house to yet another California disaster—mud slides. (Plants shorter than 18 inches are allowed near the house. Well-watered flowers and succulent plants are recommended.) But bare earth doesn't stay bare; weedy annual grasses sprout fast, and when they die back, they're exceedingly flammable.
Beyond the idea of succulent plants—things like sedums and cacti that store water in their thick fleshy tissues—experts don't agree on what plants would be especially helpful. There is agreement (PDF) on what trees to avoid—junipers, pine trees, eucalyptus, and Italian cypress. Unhappily, pine trees and cypresses happen to be the particular favorites of the owners of Mediterranean-style luxury homes. (Here's more information on what not to plant and a map of which areas are at greatest risk.)