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Master Gardener Journal  


P R E V E N T I O N



The Fire-Resistant Landscape

by Linda A. Guy,
Master Gardener


Communities in Arizona's high country continue the long rebuilding process after last summer's heartrending wildfire losses. Sadly, too many of us believe that wildfire is a risk only to those residing in the heavily forested areas of our state. In fact, any vegetation is potentially combustible, particularly in the arid southwest. People with homes and vacation properties in high chaparral, brush, or grasslands, or simply in suburban foothills ill-served by distant fire departments, are well advised to examine their property's susceptibility to fire, develop a protection plan, and implement improvements working outward from the major buildings. The question is not if a wildfire will ever occur, but when.

Missoula, Montana

A building's ability to withstand the ravages of wildfire is determined principally by: (1) the selection of the roofing material, and (2) the use of a defensible space plan around the structure. When considering major roof repairs or replacement, fire-resistant materials should be researched and municipal building departments should be consulted for minimum specifications. Choose the most fireproof material you can afford.

A defensible space plan outlines action steps in each of three management zones on a property. These are areas where vegetation and fuels are actively managed or eliminated to reduce the intensity and spread of fire to and between buildings, or from burning buildings to adjacent range or forest. In general, this means that landscaping around a home is lower growing, more widely-spaced, incorporates noncombustible groundcovers such as gravel and stone, and gives priority to native plant material. Do not underestimate the importance of executing such a plan for your property: firefighters may bypass your home, choosing to protect structures where they are more confident of both their safety and their ability to manage the fire.

The first zone is the area immediately around the house and all other detached structures. Measured from overhanging eaves and/or decks, it should extend at least 15 feet; 30 feet is recommended in the chaparral. This should be the area where you address most of your efforts. Propane tanks and stacks of firewood should be relocated from here to Zone 2.

Missoula, Montana Summer 2000
Photo courtesy of John McColgan, Bureau of Land Management
Firewide


Ideally, there are no trees in Zone 1. If they cannot be removed, treat them as a part of the building and extend the perimeter of this first zone accordingly. Prune these trees to at least 10 feet above ground; also prune all branches that are within 10 feet of any building or chimney. Smaller shrubs and other materials that can act as a 'ladder fuel' under Zone 1 trees should be removed.

Other plantings in Zone 1 should be 3 to 5 feet from the house perimeter. This includes turf. Decorative gravel, stone, or brick can be used in these areas, including the ground beneath decks, which should not be used for storage. Consider native groundcovers whose succulent properties make them more firewise. Resinous plant materials should be avoided near buildings. Resist large massed plantings, including wildflowers: they can be extremely combustible. Instead, create interesting, irregular islands of plant material separated by rock walls, pathways, or inorganic mulches. If organic mulches are present, use just enough to manage weed or grass growth, because thick layers tend to smolder and are harder to snuff out. Again, avoid mulches of resinous materials such as pine needles or pine bark.

Zone 2 management focuses on lowering your landscape's potential to fuel an approaching fire. This area extends at least 75 to 125 feet from structures. Trees and large shrubs are thinned to a distance of 10 feet between crowns, as measured by the closest elements of each tree's canopy, not the trunks. Vegetation on steep inclines should be thinned to a greater distance. Again, prune trees to 10 feet above ground and remove potential ladder fuels. Keep lawns trimmed to a low height and rake leaf and other litter to avoid buildup. Dispose of slash by chipping or carefully burning. The local fire or sheriff's department should have information about burning slash piles.

The last area, Zone 3, extends from the edge of your defensible space to the property line. This is treated as a transition zone to surrounding home sites or open land. Tree thinning might improve the health of your forest stand, if this is your situation. Pruning, removing dead materials, and reducing ladder fuels can improve personal safety during a period of high drought, and can help to keep trails and fire access roads clear.

More detailed information is presented in three new Firewise publications recently available from Cooperative Extension. They can be downloaded online at http://ag.arizona.edu/pubs/quarterly.html

AZ 1289 Firewise Plant Materials for 3,000 feet and Higher Elevations

AZ 1290 Creating Wildfire-Defensible Spaces for Your Home and Property

AZ 1291 Fire-Resistant Landscaping



Maricopa County Master Gardener Volunteer Information
Last Updated January 25, 2003
Author: Lucy K. Bradley, Extension Agent Urban Horticulture, University of Arizona Cooperative Extension, Maricopa County
© 1997 The University of Arizona, College of Agriculture and Life Sciences, Cooperative Extension in Maricopa County
Comments to Maricopa-hort@ag.arizona.edu 4341 E. Broadway Road, Phoenix, AZ 85040,
Voice: (602) 470-8086 ext. 301, Fax (602) 470-8092