Barbara Faurot

We live in a growing wildland-urban interface, where housing meets wildland forests and rangelands. Hotter, drier weather and higher winds create increased risk of wildfires. 

Gardeners have an opportunity to reduce the vulnerability of their homes and neighborhoods to wildfire. “Surrounding yourself with a strategically designed, lush, beautiful and well-maintained landscape is your best defense,” according to the nonprofit Idaho Firewise. 

Fire-resistant landscaping has two simple principles: Creating defensible space around the home, and smart plant selection and maintenance.

Defensible space refers to a clear area around a structure to reduce the growth of fire and provide a safety zone where firefighters can work. David Seabrook, East Jefferson District 1 Fire Commissioner and WSU Extension Master Gardener, shares some straightforward steps to create and maintain this defensible space. 

First, remove potentially hazardous materials, debris, and dead trees or shrubs near the home. Keep the roof, eaves, and gutters free of dry twigs, leaves, and needles. Store firewood and other combustible materials well away from buildings. Keep weeds and other debris away from propane tanks and sheds where gasoline or other fuels are stored. It’s also critical to have a hose or other water source easily accessible. 

If you have mature trees near the home, prune branches to about 10 feet above the ground, and 10 feet above understory vegetation. Remove tree branches within 15 feet of roofs and chimneys.

Remove “ladder fuels” — little trees that may act as ladders for fire and carry it up into the crowns of larger trees. Thinning these small trees, as well as overall woodland thinning, is best done between August and December to avoid creating a habitat for bark beetles. (The beetles become active in late winter and seek out fresh slash and damaged trees.)

If you have slash piles from pruning and thinning, chip them to decompose, or bring them to the county’s green recycling program.

“These are recommendations for gardeners to consider,” Seabrook said, adding that “each of us has to decide what risk factor we’re willing to accept, knowing that our decisions will affect our neighbors and neighborhoods.” 

Plant placement and care are just as important as plant selection. For the area within 30 feet of your house, use lower-growing, fire-resistant plants, ground covers, or well-watered turf grass mowed low to the ground. Group plants in “islands” and create fire breaks — gaps in combustible vegetation to slow the progression of a fire. These can be gravel paths, water features, rock walls, or stepping stones. 

Seabrook shared some examples at his own property. Mature trees that were growing under the eaves and near the front door were removed and replaced with smaller native rhododendrons and ground covers. Conifers within 30 feet of the house were replaced with blueberry plants. For emergency preparedness as well as fire resistance, “a nicely cultivated garden patch with food crops is a great option,” Seabrook added. 

Note that bark mulch or so-called “beauty bark” is flammable and should be replaced, if possible. Arborist chips, compost, and leaf mold are better choices to conserve moisture, improve soil, and suppress weeds, but they can smolder. 

If you do use organic mulch for its many landscape and habitat benefits, keep it at least 5 feet away from structures. Keep it moist through irrigation, and consider replacing it over time with fire-resistant ground covers. 

Inorganic mulches such as brick chips or decomposed granite are alternatives, depending on your goals. Another approach is to surround mulched areas with a fire break of gravel, rock, or other hardscape materials. 

Fire-resistant plants are not fire-proof, but when well-maintained, they are less likely to ignite and more likely to survive a fire. They have high moisture content and supple leaves, and are usually drought-resistant, requiring less irrigation. They are easy to maintain and prune, often with an open, loose branching pattern. Their stems and leaves are not resinous, oily or waxy. 

Conversely, flammable plants accumulate dry or dead material within the plant. They contain volatile waxes or oils, often with aromatic leaves and resinous sap. Examples are ornamental junipers, Leyland Cypress, Mugo pine, and shore pine. Noxious weeds Scotch broom and Himalayan blackberry are also flammable and should be removed, especially if they are near structures. 

Many recommended plants are favorite Pacific Northwest or North American natives. In addition to their fire resistance, most offer wildlife habitat and pollinator benefits. Some examples:

Low-growing natives: Arctostaphylos uva-ursi (Kinnikinnick), Fragaria species (woodland or beach strawberry), Gaultheria shallon (salal), Mahonia repens (creeping Oregon grape), Sedum spathulifolium (broadleaf stonecrop), Gaultheria procumbens (American wintergreen).

Perennials: Aquilegia formosa (western columbine), Echinacea purpurea (coneflower), Epilobium angustifolium (fireweed), Lonicera hispidula (pink honeysuckle).

Broadleaf evergreen shrubs: Rhododendron macrophyllum (Pacific rhododendron), Ceanothus gloriosus (Point Reyes ceanothus).

Deciduous shrubs: Acer circinatum (vine maple), Holodiscus discolor (ocean spray), Philadelphus species (mock orange), Ribes species (flowering currant), Symphoricarpos albus (snowberry).

Trees: Acer macrophyllum (big-leaf maple), Populus tremuloides (quaking aspen), Quercus garryana (Oregon white oak, Garry oak).

There are many popular non-native fire-resistant plants, including varieties of iris, salvia, lilac, delphinium, creeping thyme, artemisia, ice plant and other succulents, and most broadleaf deciduous trees. 

Find a research-based list of fire-resistant native and non-native plants on the East Jefferson Fire Rescue website: https://www.ejfr.org/wp-content/uploads/2020/04/FireResistantPlantsforHomeLandscapes.pdf.

Seabrook shared another important message: Despite our efforts to mitigate risk, a wildfire may occur. “Be prepared. You may be in a situation where you have to evacuate on a moment’s notice, so be ready.” 

The National Fire Protection Association is a good resource for tips on preparedness and planning: https://nfpa.org.

Master Gardeners at the online plant clinic host weekly live Zoom sessions Mondays from 12:30 to 2:30 p.m. To make an online appointment or submit a written question, visit http://jefferson.wsu.edu/plant-clinic.

(Barbara Faurot is a Jefferson County Master Gardener and Master Pruner, working with other volunteers who serve as community educators in gardening and environmental stewardship.)