Providing for Defensible Space

Fuel Reduction
The 1st goal in creating a defensible space is to remove fire-prone plants, then replant with low fuel species at appropriate densities to reduce fuel available to burn.

Sometimes, wildland vegetation and landscaping can occur as an uninterrupted cover of vegetation as opposed to being irregular or widely spread individual plants. The more continuous and dense the vegetation, the greater the wildfire threat is to your home. If this situation is present within your recommended defensible space area, you should break it up by creating separation between plants or small groups of plants.

Ladder Fuels
Vegetation is often present at varying heights, similar to rungs on a ladder. Under these conditions, flames from fuels burning at ground level can be carried to shrubs, which can ignite still higher fuels like tree branches. The ladder fuel problem can be corrected by providing a separation between the vegetation layers. Within the defensible space area, a vertical separation of three times the height of the lower fuel layer is recommended

Intelligent Landscaping
Landscaping with wildfire in mind involves plant selection based primarily on the plant's ability to reduce the wildfire threat. Minimize or eliminate the use of evergreen shrubs and trees within 30 to 50 feet of a structure, because junipers, other conifers, and broadleaf evergreens, such as eucalyptus, contain oils, resins, and waxes that make these plants burn with great intensity. Use ornamental grasses and berries sparingly because they also can be highly flammable.

Flammable Vegetation
This table lists several species of plants that generate very flammable vegetative fuel or are invasive exotic plant species. Non-recommended species include the following.

Botanical Name Common Name
Acacia (most species) Acacia
Adenostoma sparsifolium Red Shanks
Adenostoma fasciculatum Chamise
Artemisia californica California Sagebrush
Cedrus species Cedar
Cortaderia selloana Pampas Grass*
Cupressus species Cypress
Eucalyptus (most species) Gum, Ironbark
Hedera helix English Ivy*
Juniperus species Juniper
Pennisetum setaceum Fountain Grass*
Pinus species Pine
Salvia (most species) Sage
Vinca major Periwinkle*
Phoenix canariensis Canary Island Palm
Washingtonia filifera California Fan Palm
Washingtonia robusta Mexican Fan Palm

*Invasive exotic plant species commonly available from nurseries

"Fire Smart" Plants
Choose "fire smart" plants. These are plants have high moisture content and are low growing. Their stems and leaves are not resinous, oily, or waxy. Deciduous trees are generally more fire resistant than evergreens because they have a higher moisture content when in leaf and a lower fuel volume when dormant. Recommended species include the following.

Groundcovers & Low Shrubs (Under 36 Inches Mature Height)
Botanical Name Common Name
Achillea tomentosa Woolly Yarrow
Baccharis pilularis "Twin Peaks" Dwarf Coyote Brush
Cotoneaster dammeri Bearberry Cotoneaster
Delosperma 'Alba' White Trailing Ice Plant
Fragaria chiloensis Wild Strawberry
Lantana montevidensis Purple Trailing Lantana
Malephora crocea Croceum Ice Plant
Myoporum parvifolium Myoporum
Rosmarinus officinalis "Prostratus" Rosemary
Santolina chamaecyparissus Lavender Cotton
Sedum album Sedum
Senecio serpens Senecio

Groundcovers & Low Shrubs (Under 24 Inches Mature Height)
Botanical Name Common Name
Arctostaphylos "Pacific Mist" Manzanita
Baccharis pilularis "Twin Peaks" Dwarf Coyote Brush
Ceanothus griseus hor. "Yankee Point" Wild Lilac
Cistus crispus "Descanso" Rockrose
Cistus salviifolius Sage leaf Rockrose
Encelia californica Bush Sunflower
Epilobium canum California Fuchsia
Eriophyllum confertiflorum Golden Yarrow
Eschscholzia californica California Poppy
Helianthemum scoparium Peak Rush-Rose
Iva hayesiana San Diego Marsh Elder
Lotus scoparius Deerweed
Lupinus bicolor Dove Lupine
Mimulus aurantiacus Monkey Flower
Mirabilis californica Wishbone Bush
Myoporum parvifolium Myoporum
Penstemon spectabilis Showy Penstemon
Rosa californica California Rose
Rosmarinus officinalis "Prostratus" Rosemary
Salvia sonomensis Creeping Sage
Santolina chamaecyparissus Lavender Cotton
Santolina virens Green Santolina
Sisyrinchium bellum Blue-Eyed Grass
Trichostema lanatum Wooly Blue Curls
Yucca whipplei Our Lord's Candle

Botanical Name Common Name
Arbutus unedo Strawberry Tree
Ceratonia siliqua Carob
Cercis occidentalis Western Redbud
Heteromeles arbutifolia Toyon
Platanus racemosa California Sycamore
Prunus ilicifolia ssp. ilicifolia Hollyleaf Cherry
Prunus ilicifolia ssp. lyonii Catalina Cherry
Quercus agrifolia Coast Live Oak
Quercus berberidifolia Scrub Oak
Rhus lancea African Sumac
Rhus ovata Sugarbush
Sambucus mexicana Mexican Elderberry

Maintaining Defensible Space
A fire-resistant plant can lose this quality altogether if not properly maintained and irrigated. Lack of long-term attention can result in fire-resistant plants loading up with dead twigs, leaves, and branches to grow into large yet sometimes indiscernible fuel volumes. Drip irrigation, plus periodic pruning and cleaning, can maintain the fire resistance and the appearance of landscaping.

Environmental Regulations
Federal and state environmental regulations are designed to protect and preserve habitat. They may appear to conflict with fire protection planning concepts. However, environmental law should not be ignored in preparing for wildfire. Cooperation between environmental regulators, fire agencies, and property owners has allowed for clearance from existing structures for fire protection purposes only. Before any clearing is done, contact the Department of Development Services for guidance.

Collectively, fuel reduction, elimination of ladder fuels, intelligent landscaping, maintenance of low fuel landscaping, and awareness of applicable environmental regulations can provide for defensible space against wildfires.