Is Your Landscape Firewise? - March 23, 2011
Jeff Schalau, Associate Agent, Agriculture & Natural Resources
University of Arizona Cooperative Extension, Yavapai County

People living adjacent to undeveloped wildlands enjoy the solitude and closeness to nature. However, many of these settings are also wildfire-prone areas. Even established subdivisions become overgrown with time and can constitute significant wildfire risks. We should all periodically assess our homes and landscapes to determine wildfire risk factors and take appropriate action to mitigate that risk. Creating wildfire defensible space around your home reduces the vulnerability of your house and property to wildfire.

Our goal should be to develop landscapes with design and choice of plants that create wildfire defensible space and enhance outdoor living space on the property. Defensible or “survivable” space landscaping integrates traditional landscape functions with a design that reduces the threat from wildfire. It includes planting for fire safety, vegetation modification techniques, use of fire safety zones, and other defensible space principles.

Through proper plant selection, placement, and maintenance, we can diminish the possibility of ignition, lower fire intensity, and reduce how quickly a fire spreads, all of which increase a home’s survivability. Firewise plant selection is primarily determined by a plant’s ability to resist ignition thereby reducing wildfire threat. You should minimize use of coniferous evergreen shrubs and trees within 30 feet of a structure because these plants contain oils, resins, and waxes that burn with great intensity when ignited. Use ornamental grasses and berries sparingly here because they also can be highly flammable. Choose “fire smart” plants. These are low-growing plants with high moisture content. Their stems and leaves are not resinous, oily, or waxy.

Deciduous trees are generally more fire resistant than evergreens because they have higher moisture content when in leaf and a lower fuel volume when dormant, and they typically do not contain flammable oils. Placement and maintenance of trees and shrubs are as important as actual plant selection. When placing trees in a landscape, remember the tree’s size at maturity. Keep tree limbs at least 15 feet from chimneys, power lines, and structures. Small specimen trees can be used near a structure if pruned properly and well irrigated.

Defensible space landscaping uses driveways, lawns, walkways, patios, parking areas, areas with inorganic mulches, and fences constructed of nonflammable materials such as rock, brick, or cement to reduce fuel loads and create fuel breaks. Fuel breaks are a vital component in every firescape design. Water features, pools, ponds, or streams can be fuel breaks. Areas where wildland vegetation has been thinned or replaced with less flammable plants are the traditional fuel break. Boulders and rocks can be fuel breaks. Remember, while bare ground is an effective fuel break, it is not recommended as a firescape element due to aesthetic, soil erosion, and other concerns.

Homes located within chaparral vegetation or on south- or west-facing slopes pose greater risks and will require more extensive landscape planning for defensible space. Prevailing winds, seasonal weather, local fire history, and characteristics of native vegetation surrounding the site are additional important considerations.

The 30 feet closest to a structure is the most critical defensible space area. This is an area where highly flammable fuels are kept to a minimum and plants are kept green throughout the fire season. Use well-irrigated perennials here. Another choice is low-growing or non-woody deciduous plants. A lawn is soothing visually and is practical as a wildfire safety feature. However, extensive areas of turf grass may not be right for everyone. Some good alternatives include clover, ground covers, and conservation grasses that are kept green during the fire season through irrigation. Rock mulches are good choices. Patios, masonry, or rock planters are excellent fuel breaks and increase wildfire safety. You can also be creative with boulders, riprap, and dry streambeds.

Often, a representative from your local fire department or district can assist you with assessment of your property’s wildfire risk factors. The University of Arizona Cooperative Extension also has publications and information about creating and maintaining wildfire defensible space. We also have Survivable Space Educator, Mark DiLucido, available to speak to your community. Mark can be reached at 928-445-6590 ext. 231 or I also thank my colleague Joanne Skelly of University of Nevada Cooperative Extension for some of the information contained in this article.

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Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr. #C
Prescott, AZ 86305
(928) 445-6590
Last Updated: March 17, 2011
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