The Drill to Help Yard Resist Fire

Question: With the Santa Ana winds season here, I’d like to work on making my property more fire safe. What are some guidelines for making my landscape resistant to fire damage?

V.S., Fullerton

Answer: There are many preventive measures you can take.

The term “fire-resistant,” with regard to plants, can be a bit misleading. How the plants are maintained will have a great effect on how fire-retardant they are. For instance, coyote bush (Bacharis pilularis) is considered fire-resistant, but it can develop highly flammable undergrowth if not properly maintained.

How these plants are grouped and spaced is also important to interrupt the flow of fuel if a fire develops. In a high-intensity fire, everything can burn, even succulents.

The following are some ways to improve the fire safety of your property:

* Reduce the fuel load around your home. The amount of leaves, bark, twigs and branches (both dead and alive) that accumulate around a plant is what determine its fuel load.

If a plant is properly maintained, there is a high live-to-dead fuel ratio. Each late summer and fall, the moisture content of nonirrigated live vegetation goes down and the amount of dead fuel goes up.

Santa Ana winds can turn shrub tinder dry in a few hours even after irrigation.

Other factors such as insect damage and disease can also increase the amount of dead fuel. A good example of this is the oleanders dying from oleander leaf scorch.

To reduce fuel load, cut tall grass and weeds to the ground and prune dead growth from trees and shrubs--paying special attention to the undergrowth, which may be masked by a thin layer of green on top.

Also thin California natives such as toyon, lemonade berry bush, buckwheat and California sagebrush that tend to develop dead underbrush.

* Keep the roof and gutters free of leaves, pine needles and other debris. Remove dead limbs that overhang the roof or are within 10 feet of a chimney.

* If there is an area on or off your property with overgrown weeds, brush or other hazardous debris, contact Orange County’s Hazard Reduction and Weed Abatement Program at (714) 447-7108.

If brush disposal is a concern, consider county landfill locations such as Prima Deshecha Sanitary Landfill in San Juan Capistrano, Olinda Alpha Sanitary Landfill in Brea or private green waste facilities that accept green waste and wood for a small fee. Two such facilities are Aguinaga Fertilizer in Irvine ([949] 786-9558) and Tierra Verde in San Juan Capistrano ([949] 728-0401).

* If your property is large or you live in a residential area that borders a natural ecosystem (urban-wildland interface), create a 100-foot defensible space around your home.

Keep the area within 30 feet of your home well-watered to reduce flammability. This defensible space should be sparsely planted if possible.

Consider planting the most fire-resistant plants nearest the house (keeping the plant height of those next to the house at 1 foot, if possible).

On the property edges, progress to properly thinned and pruned native vegetation, choosing low growers that are widely spaced.

From 50 to 200 feet from your home, create islands of shrubs that are widely spaced. Allow about three to five times the plant height between shrubs.

* Avoid planting trees under or near electrical lines.

* Eliminate “fire ladders,” which are created when plants are arranged in such a way that they provide a continuous fuel supply, such as from the ground up into the tree canopy or even from a cluster of shrubs in proximity to a wood deck.

To prevent fire ladders, leave vertical as well as horizontal space between plants. Keep trees spaced 10 feet apart on mild slopes and 20 to 30 feet apart on steeper slopes.

Separate plantings of “islands” of trees and shrubs with mulch, gravel or a low-growing ground cover. To keep ground fires from spreading into trees, prune limbs of trees over 18 feet long within 6 feet of the ground. On larger trees, remove all dead and living branches to at least 10 to 15 feet above the ground. (Consult a certified arborist to assure proper pruning.)

If you have shrubs growing within the tree’s drip line, the tree’s lowest branch should be at least three times as high as the shrub.

* Remove highly flammable vegetation. The following plants are known to be flammable because of their high oil or resin content, high volume of dead fuel that accumulates in them or their reputed low moisture content in branches and leaves: Acacia, Arborvitae, California bay, bougainvillea, Carrolina Jessamine, cedar, cypress, Douglas fir, eucalyptus, fir, Hakea, Hopseed bush, juniper, New Zealand flax, pampas grass, pines (these can be a fire hazard even when they are healthy), spruce, yew, all ornamental grasses and berry vines.

Palms are highly flammable if dead fronds are not regularly removed.

If you have any of these plants and they are important to your landscape or necessary for soil stabilization, meticulously maintain them and surround them with more fire-resistant plants to reduce the danger.

Have a problem in your yard? University of California Cooperative Extension (UCCE) Master Gardeners are here to help. These trained and certified horticultural volunteers are dedicated to extending research-based, scientifically accurate information to the public about home horticulture and pest management. They are involved with a variety of outreach programs, including the UCCE Master Garden hotline, which provides answers to specific questions. You can reach the hotline at (714) 708-1646 or send e-mail to ucmastergardeners @yahoo.com. Calls and e-mail are picked up daily and are generally returned within two to three days.