What is Defensible Space?

Defensible Space is the area around a structure where combustible vegetation that can spread fire has been cleared, reduced or replaced. This space acts as a barrier between a structure and an advancing fire.

How Large Should the Defensible Space Be?

You need to clear combustible vegetation in a 100-foot radius from any structure. Your local fire agency may require you to clear additional vegetation by a written letter. You are not required to cross your property line in order to clear the 100 feet. The neighboring property owner may be required to clear the additional distance by the fire agency.

How Do I Maintain the Defensible Space?

• You may plant fire-resistant, irrigated landscaping in the first 50 feet of the 100 feet from your structure. These plants need to be maintained all year around. Note: no irrigated, or non-native landscaping is allowed within an open space easement.
• You need to keep natural vegetation in the remaining 50 feet of the 100 foot space. This would be the area furthest away from your structure. The plants need to be thinned and cut back to no more than 6 inches above the ground.
• You may need to do this several times a year since the plants grow back.
• Do not completely remove all vegetation which would leave the ground bare. Some vegetation is necessary to prevent erosion. When native vegetation is removed for fire control the bare soil is particularly vulnerable to soil erosion.
• Do not remove or disturb the existing plant root system to prevent any future erosion.
• Remove dead and dying vegetation.
• Trim trees that overhang or touch your structures.
• Properly irrigating plants will help prevent plants from igniting. Wildfires rarely occur until after June, because as little as 1 inch of water per month keeps drought adapted plants from readily burning. Permanent irrigation should be confined to landscaping within the first 50 feet of a structure.
• Trees and shrubs can be maintained by deep watering at least once a month for drought tolerant species and once a week for high water requiring plants.

What Types of Fire-Resistant Plants Should I Choose?

Generally these plants:
• Grow close to the ground.
• Have a low sap or resin content.
• Grow without accumulating dead branches, needles or leaves.
• Are easily maintained and pruned.
• Are drought-tolerant.What should I do to protect my property against fire?
• Vary the height of plants and adequately space them. Taller plants need to be spaced wider apart.
• Existing trees and large shrubs should be pruned by cutting off any branches up to 6 feet above the ground to prevent ground fires from spreading upwards into trees.
• For fire truck access, remove vegetation within 10 feet of each side of your driveway.
• Remove any tree limbs within 10 feet of your chimney.
• Work with your neighbors to clear common areas between houses, and prune areas of heavy vegetation that are a fire threat to both properties.
• Avoid planting trees under or near electrical lines. They may grow into or make contact with overhead lines. Under windy conditions these instances may cause a fire.
• If you have a heavily wooded area on your property, removing dead, weak or diseased trees may improve growing conditions. This will leave you with a healthy mixture of both new and older trees.
• Any removed trees may be chipped and left on your property if they don’t present a fire hazard. Contact your local fire agency to find out how to do this.
• Don’t forget to legally dispose of all your cut vegetation. You may contact your local landfill to inquire about green waste recycling. Open burning may not be allowed. Contact your fire agency for more information.
• Stack firewood and scrap wood piles at least 50 feet from any structure and clear away any combustible vegetation within 10 feet of the piles. Many homes have “survived” as a fire moved past it, only to burn later from a wood pile that caught fire after the firefighters had moved on to protect other homes.
• Check and clean your roofs and gutters on all structures several times during the spring, summer and fall to remove debris that can easily ignite from a spark.

Acceptable Plants for a Defensible Space in Fire Prone Areas

All plants on the following list are considered drought-tolerant in the climate zone indicated. However, remember that no plant is totally fire resistant. Drought-tolerant plants are trees, shrubs, ground covers, and other vegetation that can grow and reproduce with only natural moisture such as rainfall. Occasional irrigation is necessary only in extreme drought situations. Plants that are indicated by the “R” are the least drought-tolerant plants on the list. These plants grow best in riparian areas. Riparian areas can be described as areas where the water table is very near the surface of the ground. Although the ground may be dry, the plants growing there will be green and lush all year around.

When first planting drought-tolerant plants, you need to water deeply to encourage the roots to find natural moisture in the soil. This type of watering needs to continue for at least three years. More water should be provided in summer and less (if any) in the winter. After three years, you should be watering the plants less and depending more on the natural rainfall to provide moisture. Plants on the list which are noted with ** are San Diego County native or naturalizing plant species. These are types of plants native to or brought into the San Diego County area. These plants are able to grow and reproduce in the local climate and the natural rainfall is enough moisture.

Defensible Space Works

During the 2003 raging California fires, a number of homes were saved as a result of the owners’ careful pruning and landscaping techniques that protected their homes. In a fire situation, the dead trees and shrubs surrounding your home act as fuel for fire. Removing flammable vegetation reduces the threat of fire. Follow these basic rules to create defensible space that works.
• Remove all dead plants, trees and shrubs from the site.
• Reduce excess leaves, plant parts and low-hanging branches.
• Replace dense flammable plants with fire-resistant plants.
• The choice of plants, spacing and maintenance are crucial elements in any defensible space landscaping plan. Tips for a Fire-safe Landscape
• Create a defensible space perimeter by thinning trees and brush within 30 feet around your home.
• Beyond 30 feet, remove dead wood, debris and low tree branches.
• Eliminate small trees and plants growing under trees. They allow ground fires to jump into tree crowns.
• Space trees 30 feet apart and prune to a height of 8 to 10 feet.
• Place shrubs at least 20 feet from any structures and prune regularly.
• Plant the most drought-tolerant vegetation within three feet of your home and adjacent to structures to prevent ignition.
• Provide at least a 10 to 15 foot separation between islands of shrubs and plant groups to effectively break-up continuity of vegetation.
• Landscape your property with fire-resistant plants and vegetation to prevent fire from spreading quickly. Choose Fire Resistant Materials
• Check your local nursery or county extension service for advice on fire resistant plants that are suited for your environment.
• Create fire-safe zones with stone walls, patios, swimming pools, decks and roadways.
• Use rock, mulch, flower beds and gardens as ground cover for bare spaces and as effective firebreaks.
• There are no “fire-proof” plants. Select high moisture plants that grow close to the ground and have a low sap or resin content.
• Choose plant species that resist ignition such as rockrose, iceplant and aloe.
• Fire-resistant shrubs include hedging roses, bush honeysuckles, currant, cotoneaster, sumac and shrub apples.
• Plant hardwood, maple, poplar and cherry trees that are less flammable than pine, fir and other conifers. Maintain Your Home and Surrounding Property
• Maintain a well-pruned and watered landscape to serve as a green belt and protection against fire.
• Keep plants green during the dry season and use supplemental irrigation, if necessary.
• Trim grass on a regular basis up to 100 feet surrounding your home.
• Stack firewood at least 30 feet from your home.
• Store flammable materials, liquids and solvents in metal containers outside the home at least 30 feet away from structures and wooden fences.
• No matter where you live, always install smoke alarms on every level of your home. Test them monthly and change the batteries at least once a year. Consider installing the new long-life smoke alarms.