Fire-resistant landscaping for your home garden | Garden Notes

Barbara Faurot

We live in a growing wilderness-city interface, where living meets wild forests and pastureland. Hotter, drier weather and stronger winds increase the risk of forest fires.

Gardeners have the opportunity to reduce the vulnerability of their homes and neighborhoods to wildfire. “Surrounding yourself in strategic, lush, beautiful, and well-manicured scenery is your best defense,” according to the Idaho Firewise nonprofit.

Fire retardant landscaping has two simple principles: creating a defensible space around the home and smart plant selection and care.

Defensible space refers to an open area around a structure to reduce the growth of fire and provide a safety zone for firefighters to work in. David Seabrook, East Jefferson District 1 Fire Commissioner and WSU Extension Master Gardener, shares some simple steps in creating and maintaining 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 away from buildings. Keep weeds and other debris away from propane tanks and sheds that are used to store gasoline or other fuels. It is also important that a hose or other source of water is easily accessible.

If you have old trees near the house, prune the branches to about 3 m above the ground and 3 m above the undergrowth. Remove branches within 15 feet of roofs and chimneys.

Remove “ladder fuel” – small trees that can serve as ladders for fire, and carry it into the canopy of larger trees. Thinning out these small trees, as well as thinning out the entire forest, is best done between August and December so as not to create a habitat for bark beetles. (The beetles become active in late winter, looking for freshly cut and damaged trees.)

If you have piles of lumber from pruning and thinning, chop them to decompose or take them to the county’s green recycling program.

“These are recommendations gardeners should consider,” Seabrook said, adding that “each of us must decide which risk factor to accept as we know our choices affect our neighbors and neighborhoods.”

Plant placement and care are just as important as plant selection. For the area within 9 meters of your home, use lower-growing, fire-resistant plants, ground cover, or well-watered lawn grass that is mowed close to the ground. Group plants into “islands” and create firebreaks – gaps in combustible vegetation to slow the progress of a fire. These can be gravel paths, water features, rock walls or stepping stones.

Seabrook shared a few examples on its own property. Older trees that grew under the eaves and near the front door were removed and replaced with smaller native rhododendrons and ground cover. Conifers within 9 m of the house have been replaced by blueberry plants. For both emergency preparedness and fire resistance, “a well-manicured garden with food plants is a great option,” added Seabrook.

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 for conserving moisture, improving soil, and suppressing weeds, but they can smolder.

When using organic mulch for its many landscape and habitat benefits, keep it at least 5 feet away from structures. Keep it moist with watering and consider replacing it with refractory ground cover over time.

Inorganic mulches like brick chips or decomposed granite are alternatives, depending on the destination. Another approach is to surround mulched areas with a firebreak of gravel, stone, or other hardscape material.

Fireproof plants are not fireproof, but if properly maintained they are less likely to ignite and are more likely to survive a fire. They are high in moisture, have pliable foliage, and are usually drought-resistant and require less watering. 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, combustible plants accumulate dry or dead material within the plant. They contain volatile waxes or oils, often with aromatic leaves and resinous juice. Examples are ornamental juniper, Leyland cypress, Mugo pine and coastal pine. Harmful weeds scotch gorse and Himalayan blackberry are also flammable and should be removed, especially if they are near structures.

Many of the recommended plants are popular natives of the Pacific Northwest or North America. In addition to their fire resistance, most have benefits for wildlife and pollinators. Some examples:

Low-growing natives: Arctostaphylos uva-ursi (Kinnikinnick), Fragaria species (wild or beach strawberry), Gaultheria scarlon (Salal), Mahonia repens (creeping Oregon grape), Sedum spathulifolium (broad-leaved stonecrop), Gaultheria procumbens.

Perennials: Aquilegia formosa (Western Columbine), Echinacea purpurea (coneflower), Epilobium angustifolium (Fireweed), Lonicera hispidula (pink honeysuckle).

Evergreen shrubs, Rhododendron macrophyllum (Pacific rhododendron), boast Ccanothus (Point Reyes ceanothus).

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

Trees: Acer macrophyllum (large-leaved maple), Populus tremuloides (quiver 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, as well as most deciduous trees.

A research-based list of fire-resistant native and alien plants can be found 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 best efforts to reduce the risk, wildfire can occur. “Be prepared. You may find yourself in a situation where you need to evacuate on short notice, so be ready.”

The National Fire Protection Association is a good source for preparation and planning tips: https://nfpa.org.

Master gardeners from the online plant clinic hold weekly live zoom sessions on Mondays from 12.30pm to 2.30pm. To schedule an online appointment or ask a written question, visit http://jefferson.wsu.edu/plant-clinic.

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

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