In the wake of our recent fires, I received several e-mails inquiring about the availability of fire-retardant plants.
Not too many years ago, a great deal was made of so-called fire-retardant plants. The idea was that certain plants, especially succulents such as agaves, aloes and ice plants, could slow the advance of a fire due to the high water content in their leaves. If you lived in or close to a high-risk fire area and still wanted to garden, you were supposed to find confidence in selecting plants from lists put out by various agencies _ from insurance and utility companies to fire departments _ with a vested interest in fire prevention.
An interesting note: When lists of fire-retardant plants were first drawn up in the 1990s, we had experienced several consecutive years of drought. As a result, plants listed had to be both fire- and drought-tolerant.
Today, less attention is paid to particular plants than to overall landscaping strategies _ dubbed “fire-scaping” _ designed to minimize property damage should a brush fire break out in your area.
In fact, thanks to our recent string of wet winters _ or, more precisely, snowy Sierra winters _ thinking about fire-scaping has undergone a change. As long as a drought is not imminent, it is now recommended that lawn be planted within 30 feet of houses or other structures in brush-fire areas. There are two reasons for this: First, a lawn can quickly be sprinkler-soaked in the event of a nearby fire, offering a wet blanket of security against the approaching flames; second, a lawn provides an excellent platform or staging area for firefighters. If plants of any type are grown close to a structure, it makes it difficult (when these plants catch fire) to stand your ground and combat the encroaching inferno.
As lawn alternatives, you could utilize water-saving, low-growing ground covers that remain lush and green when irrigated during the fire season, including clover, creeping potentilla and yarrow. Any ground cover that builds a layer of thatch or stems beneath the foliage _ including ivy, gazania and rosea ice plant _ is a potential fire hazard.
At 30 to 100 feet away from your house, you may keep your trees as long as the lowest branches are 10 feet off the ground. In addition, there should be at least 10 feet between the canopies or foliage domes of adjacent trees and shrubs. Trees and shrubs would also be kept severely thinned out so as to minimize accumulation of potential fuel for an approaching brush fire. In extremely hazardous areas, no plants should be allowed to grow within 100 feet of any wood-framed building.
Plants that manufacture oils or resins, California natives among them, should be avoided. The list of hazardous trees and shrubs includes eucalyptus, pine, juniper, acacia and arborvitae. In truth, every tree and shrub is potential fuel for a fire if it is placed too close to a structure or other plants or if is left unpruned or unwatered.
As long as they are well-spaced, there is an advantage to planting certain combustible natives such as toyon, manzanita and scrub oak on the fire-scape perimeter; these species, even burned to the ground, often survive a wildfire and regenerate themselves soon afterward.
A truly fire-safe landscape would be a rock garden, or perhaps a collection of a few specimen plants separated by walkways or swaths of river rock, incorporating a pool or other large water feature.
TIP OF THE WEEK: Split citrus fruit is a common phenomenon and is not a sign of disease. Split fruit is perfectly edible as long as you pick it before fungi or insects find their way inside.
Bob Triggs of Granada Hills e-mailed to ask about the cause of split fruit on his 25-year-old navel orange tree. The usual cause of split fruit is too much water. Over-irrigation of orange trees _ and of all other citrus, for that matter _ is common. Even in hot weather, citrus should not be watered more than once every other week.
When you do irrigate, water deeply by allowing a trickle of water to soak the root zone, depending on how quickly your soil drains. Splits are occasioned by rapid growth of the fruit pulp at the expense of the peel.
A sudden increase in water uptake by the tree, made possible by heavy irrigation after a dry spell or by a sudden rainstorm, could cause accelerated growth and expansion of the fruit pulp to where it splits the peel.

Photo credit: Foter.com / CC BY-SA