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Noncomustible Area:
Photo courtesy of University of California Cooperative Extension
During an intense wildfire, embers may pile up next to your home. If combustible materials are present, they may ignite and eventually produce enough heat to ignite the home.
To help reduce this risk, create a “noncombustible area” at least 3-5 feet wide around the base of your home that has a low potential to ignite from flying embers. Use irrigated, herbaceous plants (such as lawn, ground covers, and flowers), rock mulches or hard surfaces (such as concrete, brick, and pavers) within 3-5 feet of your home.
Keep this area free of woodpiles, wood mulches, dead plants, dried leaves and needles, flammable shrubs (such as juniper), and debris.
Photo courtesy of University of California Cooperative Extension
Photo courtesy of University of California Cooperative Extension
Lean, Clean, and Green Area:
Photo courtesy of livingwithfire.info
University of Nevada Cooperative Extension
Create a lean, clean, and green area that extends at least 30-50 feet from the home. "Lean" indicates the presence of only a small amount or no flammable vegetation. "Clean" means no accumulation of dead vegetation or flammable debris. "Green" implies plants are kept healthy, green, and irrigated.
Photo courtesy of California Dept. of Forestry and Fire Protection
A lean, clean, and green area serves two purposes. First, it eliminates combustible vegetation or other materials near the home that can ignite from flying burning embers. Second, if a fire does ignite, fire intensity should remain low and likely unable to generate enough heat to ignite your home. For homeowners, the lean, clean, and green area is the residential landscape that often has irrigation, ornamental plants, and regular maintenance.
Photo courtesy of California Dept. of Forestry and Fire Protection
Wildland Fuel Reduction Area:
Photo courtesy of Bureau of Land Management
The ”wildland fuel reduction area” usually lies beyond the “lean, clean, and green area” where chamise, sages, buckwheat, and other wild native and invasive plants grow.
After creating a “lean, clean, and green area” for the first 30-50 feet, County regulations encourage a wildland fuel reduction area for the remaining 50 feet for a total of at least 100 feet of defensible space. However, the recommended size for the “wildland fuel reduction area” may vary depending on the type of vegetation and slope steepness surrounding the home.
The following is recommended in the “wildland fuel reduction area.”
• Remove all dead vegetation
This should include removing all dead shrubs, dried grass, fallen leaves, etc.
Illustration courtesy of livingwithfire.infio
University of Nevada Cooperative Extension
• Thin out thick stands of shrubs and trees
Thinning will create a separation between branches. On flat to gently sloping terrain, create a separation between shrubs and trees that is twice their height.
• Thin trees to create a separation of 10 feet between the branch tips of adjacent trees.
On steeper slopes, increase the separation distance between shrubs and trees.
Illustration courtesy of livingwithfire.info
University of Nevada Cooperative Extension
• Create a vertical separation between shrubs and low-growing tree branches to prevent fire from burning into tree canopies.
Vertical separation can be created by removing low tree branches, removing or pruning the shrubs under the tree branches, or both. The separation distance should be 3 times the height of the shrubs beneath the tree branches. If there is no shrub understory present, remove low tree branches up to a height of 5 feet as burning needles, twigs, and debris lying on the ground may ignite low-growing tree branches. Never remove more than one-third of a tree’s total branches.
Illustration courtesy of livingwithfire.com
University of Nevada Cooperative Extension
To ensure you create adequate defensible space, consult your local fire authority and vegetation, brush management or weed abatement code.
Six Steps to Creating Effective Defensible Space -
Introduction:
The term “defensible space” refers to the area around a structure where the vegetation is managed to reduce the intensity and spread of wildfire. Defensible space also provides firefighters a safer space to defend the house. If firefighters are not available, defensible space improves the likelihood a structure will survive without assistance.
Photo courtesy of livingwithfire.info
University of Nevada Cooperative Extension
Unfortunately, some homeowners associate defensible space with a large expanse of bare ground surrounding their home. While bare ground is certainly fire-resistant, it is unacceptable for aesthetic reasons and can contribute to soil erosion. Homeowners can have both an attractive landscape and an effective defensible space.
Photo courtesy of livingwithfire.info
University of Nevada Cooperative Extension
Step 1: Measure and mark out a defensible space zone.
Measure and mark out a defensible space zone. The size of the defensible space zone is usually expressed as a distance extending outward from the house in all directions.
County regulations generally require 100 feet of defensible space around a structure, however, local fire authorities may require greater distances in some higher risk situations. Homeowner insurance companies may also require greater distances to qualify for coverage. Exceptions for a defensible zone less than 100 feet can be officially granted by local fire authorities if a structure complies with enhanced fire-resistive construction standards.
Photo courtesy of livingwithfire.info
University of Nevada Cooperative Extension
If the defensible space zone exceeds your property boundaries, seek permission before doing work on another property, or ask neighbors to also join in creating defensible space. Also check to ensure your property is not located in a protected area with special land management regulations. The effectiveness of a defensible space zone improves when entire neighborhoods participate.
Photo courtesy of livingwithfire.info
University of Nevada Cooperative Extension
The next five steps apply to the vegetation growing within this area.
Step 2: Remove dead vegetation.
Dead vegetation includes:
• Dead and dying trees or parts
of trees
Photo courtesy of Karla Vega, NRCS
• Dead native and ornamental shrubs
Photo courtesy of livingwithfire.info
University of Nevada Cooperative Extension
• Dead grass, weeds, and flowers
• dead leaves, needles, and twigs that
are still attached to plants, draped on
live plants, or lying on the ground
Photo courtesy of University of California Cooperative Extension
Step 3: Create a separation between shrubs and trees.
Within the defensible space zone, check if native trees and shrubs, are widely spaced or occur in a dense stand. Dense stands of trees and shrubs pose a significant wildfire threat.
Photo courtesy of livingwithfire.info
University of Nevada Cooperative Extension
On flat to gently sloping terrain, pine and fir trees should be thinned to provide an average separation between canopies of at least 10 feet. For homes located on steeper slopes, the separation distance should be greater. When selecting trees for removal, consider cutting unhealthy, damaged, or weak trees.
Illustration courtesy of livingwithfire.info
University of Nevada Cooperative Extension
Dense stands of shrubs also pose a significant wildfire threat. On flat to gently sloping terrain, individual shrubs or small clumps of shrubs should be separated from one another by at least twice the height of the average shrub. For homes located on steeper slopes, the separation distance should be greater.
Illustration courtesy of livingwithfire.info
University of Nevada Cooperative Extension
For example, if the typical shrub height is 2 feet, create a separation between shrub branches of at least 4 feet by removing shrubs or pruning to reduce their height and/or diameter.
Illustration courtesy of livingwithfire.info
University of Nevada Cooperative Extension
For information on how to properly prune your trees while retaining optimal tree health download the University of California Cooperative Extension Master Gardner Tree Pruning pamphlet.
Step 4: Create a separation between tree branches and lower growing plants.
Vegetation often grows at different heights or layers, like the rungs on a ladder. For example, dried grass may be the lowest rung, shrubs the middle rung, and tree branches the upper rung. Vegetation that can carry a fire burning in low growing plants to taller plants is called “ladder fuel.”
Photo courtesy of livingwithfire.com
University of Nevada Cooperative Extension
By trimming or removing vegetation, ladder fuels can be disrupted and slow down the spread of wildfire. The recommended separation for ladder fuels is three times the height of the lower vegetation layer.
For example, if the lower vegetation layer is three feet tall, then separation between tree branches and lower vegetation should be nine feet. Separation may be accomplished by pruning lower tree branches, trimming the height of shrubs, or altogether removing lower vegetation. Never remove more than one-third of a tree’s total branches to avoid compromising tree health.
Illustration courtesy of livingwithfire.com
University of Nevada Cooperative Extension
Trim lower tree branches at least five feet off the ground, even when there is no ground vegetation below. Burning needles and twigs lying on the ground can ignite low-growing tree branches.
Photo courtesy of livingwithfire.com
University of Nevada Cooperative Extension
Step 5: Create a lean, clean, and green area.
Create a lean, clean, and green area in the first 50 feet of the total 100 feet required for defensible space around your home. In the remaining 50 feet, native vegetation may be used but it must be thinned at least 50%.
For most homeowners, the lean, clean, and green area is their residential landscape. This area is often irrigated, planted with ornamental vegetation, and regularly irrigated and maintained.
Photo courtesy of Rancho Santa Fe Fire Protection District
A lean, clean, and green area has two goals:
1) to eliminate combustible materials and vegetation near the house that can ignite from flying embers and
2) if a fire does ignite, fire intensity should remain low and likely unable to generate enough heat to ignite your home.
Consider these fire-smart tips for creating a lean, clean, and green area within 50 feet of your home:
Although various landR-SA">
Photo courtesy of livingwithfire.info
University of Nevada Cooperative Extension
Lawns are a good choice for this area; however, consider planting a variety that does not require frequent watering or mowing to remain healthy and maintained.
Highly flammable wildland plants should be removed or replaced. If you wish to retain a few, keep them free of dead wood and leaves, prune to reduce the amount of fuel, and separate from other wildland vegetation.
Clear all flammable vegetation from within 10 feet of firewood stacks, propane and other fuel tanks, and water tanks.
Trim tree limbs touching the house or deck, overhanging the roof, encroaching on power lines, and from within 10 feet of the chimney.
*For more information on pruning or remvoing trees that threaten safety and the reliablility of your electric system visit the SDG&E Tree Smart Program website at, http://www.sdge.com/safety/trees/shtml
Flowers, including perennials, annuals, succulents, and bulbs, are good choices as long as they are actively growing. When they start to dry out and turn yellow, dead leaves and flowers should be removed.
Photos courtesy of Mission Trails Regional Park, www.mtrp.org
Deciduous is better than evergreen. Many evergreen shrubs and trees contain flammable oils and resins that burn very hot when ignited.
Keep deciduous trees well-maintained. Plant deciduous trees to allow at least a 10-foot separation between branch tips at maturity.
For locations and information on fire safe demonstration gardens showing type and arrangement of plants to help mitigate the risk of wildfire, click here.
Click here for a list of suggested plants for creating a defensible space from the San Diego County Department of Land Use and Planning.
Click here for a list of undesirable plants for creating a defensible space form the San Diego County Department of Planning and Land Use.
Step 6: Maintain the defensible space zone.
Maintaining a defensible space is an ongoing activity. Plants grow back and flammable vegetation needs to be routinely removed and properly disposed. Before each fire season, check your property using the previous five steps and implement the necessary defensible space recommendations.
Photo courtesy of Fire Safe Council of San Diego County
Refer to the Resources section of this website for publications and links to more information on defensible space, vegetation, and landscaping for fire safety.
Photo courtesy of Karla Vega, NRCS 
Photo courtesy of Fire Safe Council of San Diego County
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