Fire, Defensible Space, and You...

Many portions of the unincorporated areas of the County of San Diego share expansive, rural settings of native plant life.  Fire is an important factor in maintaining the healthy status of these native plant species.  Since these areas are also highly desirable places in which to live, maintaining a defensible fire space around structures is essential, and required, for protection against fire.  This information will provide you with some helpful hints to assist you in defending your property.

During the October 2003 Firestorms, it was painfully evident that there was insufficient "Defensible Space" on many properties which contributed to destroyed homes and other structures.  As a result, the County of San Diego has amended an ordinance that requires residents to keep their property free of fire hazards: including certain vegetation types, green waste and rubbish.  Residents can comply with this ordinance by creating a "Defensible Space" around their homes and by taking other preventative steps on their property.

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?

Please reference form PDS 199 for more information.  Generally though, use plants that:

  • 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.

HOW DO I CLEAR LEGALLY?

Combustible vegetation can only be removed by mowing, cutting and grazing as long as the root structure is left intact. Any trees you remove shall have the stumps cut no higher than 8 inches above the ground. The only exception would be an orchard. Orchard trees may have their stumps completely removed. For answers to Frequently Asked Questions about clearing, please read Fire Clearing FAQ Sheet.

CAN I CLEAR INTO OPEN SPACE?

If an open space easement is located on your property you may legally clear the 100 feet from your structure, even if it takes you into that easement, upon written authorization of your fire protection district.  No irrigated, or non-native landscaping is allowed within an open space easement.  Also, please read the Fire Clearing FAQ Sheet for simple answers to questions about clearing brush.

WHAT IS COMBUSTIBLE VEGETATION?

Combustible vegetation is any material that left in its natural state will readily ignite, burn and cause fire to move to any structure or other vegetation.  This would include dry grass, brush, weeds, litter and waste.  This would not include fire resistant landscaping some of which can be found in the "Suggested Plant List For Defensible Space" later in this handout.

OTHER PRECAUTIONS TO CONSIDER

WHAT TYPES OF PLANTS SHOULD I AVOID PLANTING ON MY PROPERTY?

Included in this handout you will find an extensive list of plants that you should avoid. These plants and trees burn easily since they have large amounts of oil, sap, rough bark and other material that is flammable.

WHAT ELSE 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 listed on the page 4 of form PDS 199 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.

Click the image for a detailed map

FIRE AGENCY CONTACT LIST

Please see the San Diego County Fire Authority Fire Agency Contact List for contact information.
Planning & Development Services, General Information (858) 694-2960
County Farm and Home Advisor (858) 694-2845
Insurance Information Network of California -- Brochures or call (800) 397-1679

REFERENCES

AFTER A FIRE

It is urgent to temporarily stabilize any slopes on the property prior to the winter rainy season (November 11 - April 30).  Rains can cause slope failure and mudslides, both upstream from you, and downstream to your neighbor.  Some preventive methods that can be used singly, or in combination with each other are:
 

  • Plastic sheeting - placed over the slope will divert water.  Make sure the water will flow into culverts, brow ditches or other diversions.
  • Straw mulch blankets
  • Jute mesh
  • Wood excelsior matting
  • Geotextiles fabrics
  • Straw bale dikes
  • Straw wattles (fiber rolls)
  • Hydraulic mulching
  • Silt fences
  • Seed planting of native annuals and perennials.  No invasive, non-native species are allowed adjacent to open space areas.
  • These methods of erosion control act only as temporary measures to stabilize slopes.  If burned slopes have previously been covered with native vegetation, new plants will sprout from the underground roots.  As the rainy season progresses, other native plants will also germinate.  Man-made slopes, interior to many projects, will need to be replanted with deep rooting plant materials.  Trees and shrubs are preferred over ice plants to insure long term erosion control.

For further information, contact the California Department of Forestry and Fire Protection, San Diego Unit at 2249 Jamacha Road, El Cajon, CA 92019 (619) 590-3100, the County Department of Public Works at (858) 694-2212, or your local fire district.