Written by Alicia R.
Fire probably is the last thing most people are thinking about when entering garden centers bursting with color. But out West, where wildfire is becoming all too common, a new kind of landscape design is emerging — fire-wise landscaping.
Many California cities throughout the state are considered at risk of wildfire due to being part of wildland-urban interfaces (WUIs). These are communities that are within or close to natural open spaces that are only irrigated by rain or snow, such as chaparral lands and foothills.
Fire-wise landscaping — also called fire-safe landscaping or firescaping — relies, in part, on replacing plants that burn rapidly with fire-resistant kinds that burn more slowly. Firescaping is part of the larger defensible space strategy for protecting homes from wildfires. It discourages the rapid spread of flames and makes access to properties easier for firefighters.
Sustaining Defensible Space
Creation of defensible space is a way to buffer a home from wildfire. One aspect of the process is referred to as hardening your home, which the California Department of Forestry and Fire Protection (Cal Fire) explains at its Ready for Wildfire website.
Hardening involves basic modifications — some as expensive as reroofing with fire-resistant materials and others as modest as maintaining water hoses reaching all sides of a house and other flammable structures, such as fencing. Hardening a property also includes trimming trees and shrubs bordering roads and driveways so firetrucks can reach your property.
Another aspect of defensibility that the website details is division of the area surrounding a house into two firescaping zones, one 30 feet away (zone 1) and the other (zone 2) at 100 feet. Here are some tasks by zone.
- Weed and remove dead plant material
- Clean up debris on roofs and in building gutters
- Prune trees so branches don’t overhang roofs
- Trim trees so their canopies are ten feet apart
- Remove or prune plants near windows
- Trim annual grasses (ornamentals and wild grasses) so they’re no taller than four inches
- Continue 10-foot horizontal spacing of trees on flat ground and increase distances on slopes (20 to 30 feet depending on steepness)
- Avoid laddering (the potential for flames to leap up trees from other vegetation) by pruning bottom branches so they are six feet above ground or even higher if there is a shrub near the tree.
Fire-resistant hardscaping and plants are the other components of designing defensible space.
Choosing Hardscaping Materials and Mulch
Water features, patios, and pathways are examples of hardscaping. They beautify a yard and can also aid fire resistance if strategically designed to create barriers between plant groupings.
Noncombustible materials, such as gravel, stone, and brick are especially successful in slowing a wildfire’s progress through a yard’s vegetation. Features such as gravel paths, dry river beds constructed of cobblestones, and masonry or stone walls or raised planters.
Gravel mulch is another hardscape feature. It works particularly well for drought-resistant plants, like sages and succulents, which can develop fungal problems from organic mulches that need to be kept damp to decrease their flammability in fire-wise landscapes.
University of California Division of Agriculture and Natural Resources advises that bark and wood mulches not be used within about five feet of foundations. It suggests rock mulch close to your house and other flammable structures. If you use wood or bark mulch further away from structures, UC notes that larger chunk varieties are slower to ignite. However, it adds that “thick mulch layers (greater than 2 inches deep) tend to smolder and are difficult to extinguish.”
Discovering that Water Wise is Fire Wise
Many wildfire resource websites note that many low-water or “water-wise” plants are successful at resisting fire. That’s what environmentalist Patti Prairie had heard before building her Montecito home in 2011. Then the huge Thomas Fire struck in December 2017, and she discovered that it was true.
Writing at her Landscaping Water Wise website, Prairie said that most of her landscaping and outbuildings were destroyed when a fire cyclone “whipped up by 65-mph winds raced down our lane.”
The fire destroyed two houses to the north of the Prairie’s property, but firefighters told them their landscaping helped in stopping it 10 to 20 feet away from Prairies’ home. Prairie says that plump-leafed succulents, such as various agaves, were a key defense along with horizontal and vertical spacing of plants, gravel and stone hardscape, fire-resistant building materials, and availability of garden hoses.
Succulents and cacti are go-to, drought- and fire-resistant choice largely due to high moisture content.
Selecting Fire-Resistant Plants
Some trees are like torches that flare almost immediately when fire comes their way. Wildfire specialists particularly recommend avoiding species high in oils and resins, such as acacia, eucalyptus, juniper, and pines.
But any shrub can be a fire hazard if grown close to window or under an eave, especially near a vent that can lead fire inside a house. This is even true of some water-wise plants, such as rosemary, which has the dense, needle-like leaves that fire experts say to avoid.
Lists of fire-resistant choices are available online. Here are some examples:
- Fire-Resistant Plants for Home Landscapes (Oregon State University, Washington State University, University of Idaho)
- Fire Resistant Plants (FireSafe Marin)
- Fire Resistant Native Plants with High Wildlife Value (Theodore Payne Foundation)
- Plants with a Favorable Fire Performance Rating (Diablo FireSafe Council)
You may discover some disagreement among these lists. What is highly flammable in one location may be less so in another due to different climate and weather conditions.
Here are some choices we sell that are generally considered to be both water wise and fire wise. They may not be available at all of our Green Thumb Garden Centers at the same time, but we’ll work with you to provide what you need.
Plants for Firescaping
(The California Native Plant Society’s CalScape database is a good source for pictures.)
- Western Redbud (Cercis occidentalis) — mostly available in spring
- Toyon (Heteromeles arbutifolia)
- California Lilac (Ceanothus spp.) — some of the types shown here
- Coyote Brush (Baccharis pilularis)
- Monkeyflower (Mimulus )
- Oregon Grape (Berberis acquifolium)
GROUNDCOVERS & PERENNIALS
- Agave (Agave spp.), Ice Plant (Delosperma spp.), and other succulents
- Cacti of many kinds
- Carpet Bugle (Ajuga)
- Lambs Ears (Stachys byzantina)
- Tickseed (Coreopsis)
Need More Information?
Green Thumb sells a wide variety of plants appropriate for water-wise and fire-wise gardening at our five nurseries (Canoga Park, Lake Forest, San Marcos, Santa Clarita, and Ventura). If you are curious about any of the plants you see in our centers or about ones in the lists we mentioned here, we’ll be glad to share what we know. Contact us today for help creating a lovely, fire-safe garden.
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