Firesafe Gardening and Landscaping
Researched by SCMG Steven Hightower
The Department of Forestry recently stated that this could be one of the worst fire seasons in a long time. With wildfires a constant threat in summer and fall in California, it's only prudent for homeowners to consider fire safety when creating a landscape design, or planning a garden. This of course applies even more so to those who live in rural and woodland settings, especially those on slopes atop wooded canyons. Fortunately, it’s possible to have landscaping around the home that is both more fire-safe, and good looking--and even drought tolerant, too. We'll concentrate on two topics in this article--general fire safety principals as regards landscaping--safe zones and the like; and plant selection and plant placement for fire-safe gardening.
General fire safety: Two Zones
Excess fuel, such as grass, brush, closely packed shrubs, woodpiles, and flammable debris in its proximate area are the greatest risk for a home in the event of a wildfire. California state law requires a 100-foot 'defensible space' around your home, which consists of two zones--the immediate 30 feet around the structure the state calls ‘Lean, Clean and Green Zone’, and a further 70 feet is referred to as a ‘Reduced Fuel Zone’. Extending that defensible space if you're high on a hillside is prudent (fire travels uphill much more rapidly than on flat ground), and there are formulas to calculate such distance. The stated goal of this defensible zone is to "protect your home while providing a safe area for firefighters." Investigations of homes that were threatened by wildfire have shown that houses with an effective defensible space are much more likely to survive a wildfire. Sudden Oak Death has increased the excess fuel load in some areas, and Fire Safe Sonoma has a program www.firesafesonoma.org/whats_new.htm that can provide funds for homeowners and neighborhood groups to assist with the cost of excess fuel (e.g. dead trees!) removal.
What does Lean, Clean and Green involve?
This close-in zone is meant to prevent the spread of fire from plant to plant, and then to the house. The code requires that all flammable material within this zone be removed, with the exception of individual trees and shrubs that are 'well spaced and well pruned'. This means that things such as firewood, compost piles, building materials, woodpiles, stacks of paper, and the like cannot be within 30 feet of the house. Some of the worst culprits can be items that we don’t think of as dangerous, such as empty plastic nursery pots. Plants within that zone should be well spaced, not too tall, and selected from plant types that are higher in moisture and lower in oils than normal--more on plant lists later.
What you don't want to do is provide a 'fire ladder' to your eaves and roof--dense plants, increasing in height toward the house, that will lead fire right up to the structure. Much safer is to have lower plants closer to the house, with some height increasing as you move out. Tree branches must be pruned 10 feet back from any chimney, and all chimneys must have spark arrestors. Hardscape in the zone, such as gravel, decomposed granite, stone patios and water features increase the fire safety of your home.
Other important tips in the close-in zone:
Keep trees pruned back from the roof, and remove any dead branches hanging over structures.
The Reduced Fuel Zone
Depending on where and in what environment you live, complying with all of these rules and suggestions can be difficult, and perhaps impossible without creating somewhat of a scorched earth look. There is a balance between aesthetic and safety, taking into consideration the probability level of a fire running through your particular area that must be considered. For example, I live on seven acres of oak woodland on the slopes of Sonoma Mountain. Most of the close-in requirements are met (I do need to re-prune some tree branches near the roof)--the roof is tile, the chimneys have spark arrestors, the plant mix doesn't contain much in the way of proscribed species, and there is quite a lot of hardscape with gravel, rock walkways and flagstone patios. But a couple of requirements aren't practical or desirable for me. For example, to thin to a 15 foot space between crowns of trees within 30 feet of the house, would mean removing at least half the trees.
Now on to plant selection. Any plant will burn with enough heat. But some, known as pyrophytic plants, burn much more readily. These plants are high in volatile oils, waxes or resins, contain a lot of fine, twiggy dry material, may have loose or papery bark, or have stiff, woody branches and fine or lacey leaves. They burn much more readily than others, often tending literally to burst into flame. Good examples of such plants to avoid include eucalyptus, cypress, manzanita, Douglas fir and other conifers and needle-leafed evergreens, especially juniper. Ray Moritz, a consulting arborist and fire ecologist who does a lot of work in Sonoma County, says juniper burns "like a pile of old tires" and firefighters have been known to call it the gasoline plant.
Fire-safER plants tend to have a higher moisture content and be lower growing. Examples include dwarf ceanothus, yarrow, rock-roses, creeping rosemary, lavender, santolina, alyssum, and salvia. Of course succulents are very fire-safe, due to their very high water content. Many fire-safe plants can also be relatively drought tolerant, and provide a very attractive palette as well. Landscape layout of trees, shrubs and perennials is as important as actual plant selection (always keep a plant's ultimate size in mind). Plant them far enough apart so they don’t “create a big fireball” if one catches fire. Integrate hardscape elements for plant separation--flagstone, gravel, decomposed granite, rock walls and other non-flammable elements, all of which can add to the garden aesthetic, as well as being safer. The FireSafe Sonoma guide states "A fire-safe landscape lets plants and garden elements reveal their innate beauty by leaving space between plants and groups of plants. In fire-scaping, the open spaces are more important than the plants."
Rubus Pentalobus calycinoides “Emerald Carpet”
Correa “Carmine Bells”
Thymus pulegioides “Archer’s Gold”
Verbena bonariensis patagonica
Teucrium cossonii Germander and fruticans Bush Germander
Asteriscus maritimus “Gold Coin”
Alyssum “Snow Crystals”
Olive “Majestic Beauty”
Arbutus “Strawberry Tree”
MODERATE TO LITTLE WATER
Leonotis Leonorus Lion’s Tail
Atriplex lentiformis Salt Bush
Achillea “Fireland” Yarrow
Coreopsis “Flying Saucers”
Agapanthus “New Blue”
Lavender dentate candicans
Kniphofia “Torch Lily”
Penstemon heterophyllus “Blue Springs”
Armeria maritime Common Thrift
Salvia clevelandii “Alan Chicking”
Salvia “Bees Bliss”
Rosemarinus “Tuscan Blue”
Santolina chameacyparissus “Nana”
LITTLE TO NO SUMMER WATER
Rhamus californica “Mound San Bruno”
Artemesia “Powis Castle”
Ceanothus glorious horizentalis “Yankee Point” and “Carmel Creeper”
Arctostaphylos uva-ursi “Emerald Carpet” Manzanita
Fremontodendrom “San Gabriel”
Dodonaea viscose Hopseed Bush
Solanum jasminoides Potato Vine
Erigeron Santa Barbara Daisy
Centranthus ruber Jupiter’s Beard
Salvia greggii “Lipstick”
Salvia sonomonsis Creeping Sage
Zauschneria California Fuchsia
Aloe brevifolia variegate
Opuntia micodasys and “Santa Rita”
Sedum brevifolium, confusum, rupestris “Angelina,” spurium “Red Carpet,” “Autumn Joy” and telephium
Additional information on firesafe landscaping is available at Firewise.org and FireSafe Sonoma.
FireSafe Sonoma has produced a guide called ‘Living with Fire in Sonoma County’ that can be downloaded from their website.
There are also University of California publications available on the topic: UCANR Publications 8322--Landscaping Tips to Help Defend Your Home from Wildfire and 8228--Home Landscaping for Fire.
©Sonoma County Master Gardeners