In the Pacific Northwest, fires are a natural part of the changing landscape, and homeowners must take special precautions to protect their lives, homes, and property. As we map out our gardens for this year, Amy Jo Detweiler and Stephen Fitzgerald of Oregon State University Extension Service give us their advice for designing a safe, smart, firewise landscape.
When landscaping around a home, most homeowners are interested in creating a landscape that is aesthetically pleasing, complements their home, and has variations in color, texture, flowers, and foliage. When selecting plants, you also should consider the flammability of plants (i.e., fuel), particularly if your home is located in or adjacent to a forest or rangeland.
Homeowners should take active steps to minimize or reduce the fuel and fire hazard around their homes, including the use of fire-resistant plants in the landscape. Equally important is proper plant placement, plant spacing, and ongoing plant maintenance. These practices, when combined, can create a fuel break and help protect your home by blocking intense heat.
Flammable plant material in your landscape can increase the fire risk directly around your home. The 1991 Oakland Hills fire in California is a prime example of how flammable plant material (Eucalyptus trees) can act as fuel and contribute to the intensity of a wildfire. More than 3,000 homes were destroyed in that devastating wildfire.
What are fire-resistant plants?
Fire-resistant plants are those that do not readily ignite from a flame or other ignition sources. These plants can be damaged or even killed by fire; however, their foliage and stems do not significantly contribute to the fuel and, therefore, the fire’s intensity.
Fire-resistant does not mean fireproof
There are several other significant factors that influence the fire characteristics of plants, including plant moisture content, age, total volume, dead material, and chemical content.
Plants that are fire-resistant have the following characteristics:
• Leaves are moist and supple.
• Plants have little dead wood and tend not to accumulate dry,
dead material within the plant.
• Sap is water-like and does not have a strong odor.
• Sap or resin materials are low. Most deciduous trees and shrubs are
In contrast, plants that are highly flammable generally have several of these characteristics:
- • Contain fine, dry, or dead material within the plant, such as twigs, needles, and leaves.
• Leaves, twigs, and stems contain volatile waxes,terpenes, or oils.
• Leaves are aromatic (strong odor whencrushed).
• Sap is gummy, resinous, and has a strong odor.
• May have loose or papery bark.
Notes on selecting fire resistant plants
There is a wide array of trees and other plants from which to choose that are both attractive and fire-resistant. Our publication (see link below) provides a diverse list of plant material divided into perennials, groundcovers, trees, and shrubs that are adaptable to several regions in the Pacific Northwest and other western states. Check with your local Extension office or a nursery to find out which plants are adaptable to your area.
Annuals can be part of a fire-resistant landscape if well watered and well maintained.
A well-maintained lawn can be included in a fire-resistant landscape and serves as an effective fuel break. For more information on lawn care and maintenance, ask for publications from your local Extension office.
- Hardiness zones
When you are selecting plant material for your landscape, be sure to choose plants that are adaptable to your area and right for your hardiness zone. Remember to think about the microclimates that exist in your community and your own back yard. Check with your local Extension office or a garden center to find the correct hardiness zone for your area. This information will assist you in buying more adaptable plant material for your landscape. To view the USDA hardiness zone map, go to USDA.gov.
Bark mulch is often used in home landscapes. However, firebrands from a wildfire or cigarettes can ignite dry bark mulch, conveying the fire to your home. If you landscape with bark mulch up against your home, make sure it remains moist to prevent ignition. You may also consider using less flammable types of mulch, such as gravel or decorative rock, or a combination of wood bark mulch and decorative.
Pacific Northwest Extension — Oregon State University, Washington State University, and the University of Idaho — produced a comprehensive list of firewise landscape plants, complete with color photos! Download your copy of Fire-Resistant Plants for Home Landscapes. (It’s a big doc, so be patient.)
For more on fire-safe planting and landscaping, visit Firewise USA.