Gardening Articles

Defensible Space and Fire-Resistant Landscaping


Wildfires swept through parts of San Diego County in May 2014, yet a smaller percentage of homes and other structures were lost than in the wildfires of 2007 or 2003. Repeatedly that was attributed to not only better communication and use of resources between the different agencies helping fight the fires, but to homeowners’ use of defensible space and fire resistant gardening. What does defensible space mean? How does fire-safe gardening differ from just keeping the landscape cleared of debris?

Cal Fire defines defensible space as “the buffer you create between a building on your property and the grass, trees, shrubs, or any wildland area that surround it. This space is needed to slow or stop the spread of wildfire and it protects your home from catching fire – either from direct flame contact or radiant heat. Defensible space is also important for the protection of the firefighters defending your home.”

In 2005, California state law extended the defensible space clearance around homes and structures from 30 feet to 100 feet. Defensible space is broken into two zones. Zone 1 is the first 50 feet around a structure in San Diego County, and Zone 2 is the remaining of the 100 feet clearance.

Some of the points of a defensible space are common sense: use fire-resistant building materials for the roof and structure, keep screen mesh over chimneys as is required by law, and remove branches from touching the house and keep them a minimum of ten feet away from chimneys. Properly maintain lawns and other landscaping and remove dead branches, brush, and weeds. Roofs and rain gutters must be clear of dry leaves and pine needles. We had to remove a 50 year-old pine tree from our yard, or our house insurance would have been cancelled because needles were on the roof between cleaning sessions.

Other defensible points are less obvious. Firefighters need room to maneuver so they can fight a fire safely. Plants that are flammable should be removed or pruned around windows. Remove vegetation and items that can catch fire from around and under patios and decks, and separate things that can catch fire. For example, placing the patio furniture under the tree and the wood pile near the outdoor fireplace are both fire hazards. The wood pile should be relocated to Zone 2, 50 feet or more away from the house or other structure.

Landscaping for a defensible space differs from many landscape plans. Both vertical and horizontal spacing between trees, shrubs, and other plants are used to prevent fire from spreading. Instead of a tiered layering of plants from ground cover to shrub to tree, the potential fire ladder between plants is eliminated. It is recommended that trees have 5-15 feet of vertical clearance between ground level and the bottom branches. If a shrub is below a tree, there needs to be three times the height of the shrub between the lower plant and the bottom branches of the tree.

Horizontal clearance requirements differ depending on the topography of the ground and the height of the trees or shrubs. On a flat to mild slope, trees should be trimmed to keep branches a minimum of ten feet from other trees. Other plants need a spacing of two times the height between them. The spacing increases on slopes. It is recommended that trees have 20 feet between their branches on a 20-40% slope, 30 feet spacing on steeper slopes. Spacing for shrubs and other plants is four times their height on the mild to moderate slope; on slopes of greater than 40% that spacing jumps to six times the height.

Mulch helps plants maintain moisture. However, bark mulches need to be kept moist when they are close to structures or they become a fire hazard. Using gravel, decorative rock, or a combination of bark and rock is a less flammable option.

Hardscape, or the non-living part of a landscape, is fire resistant if done in noncombustible materials. Use masonry, concrete, gravel and stone for pathways, walls, decks, patios, ponds, swimming pools, and driveways. These areas can act as fire breaks and help prevent the spread of fire.


Fire-safe gardening differs from a well kept landscape by using plants that are fire resistant. No plants are fire proof, some just take longer to catch fire and burn.

Avoid plants that are highly flammable. These include plants which contain oils, gums, or resins such as eucalyptus, pines, and other conifers; plants which accumulate dead plant material such as pine, juniper, and palms; and those that have a papery or loose bark. During the Cedar fire of 2003, palm trees were torches as dead palm fronds caught fire, and groves of eucalyptus burned in Scripps Ranch. A friend of mine had her juniper plants burst into flame as she was escaping her Rancho Bernardo home during the 2007 Witch Creek Fire.

Plants that resist burning include well maintained turfs, well-watered annuals, plants with high moisture content such as ice plant, aloe, and other succulents, and plants that have little deadwood and that do not tend to accumulate dry, dead material within the plant. Look for plants whose leaves stay moist under well maintained conditions. Deciduous trees and shrubs tend to not be as flammable as evergreens. Good maintenance is needed for any plant to prevent a build-up of combustible debris. Even fire resistant plants will accumulate tinder-dry leaves and twigs and will grow beyond the recommended spacing if maintenance is neglected.

Some fire resistant plants also have low water requirements which are useful for landscaping in our dry region.  Groundcovers such as sedum and Sempervivum species are good succulent choices, while creeping thyme works well between pavers and offers summer flowers.  Perennials such as yarrow (Achillea), coreopsis, coneflower (Echinacea), Gaillardia, iris, and daylily add colorful blooms, as do shrubs of native California lilac (Ceanothus) and sage (Salvia). Other shrubs you may consider are spirea, orchid rockrose (Cistus purpureus) and shrub roses. There are many trees that are fire-resistant. Western Redbud (Cersis occidentalis), common hackberry (Celtis occidentalis), and some types of ash trees are just a few that are drought tolerant once established.

One hopes to never need to defend against fire, but by implementing a plan for defensible space and by using fire resistant plants you may get through another fire season safely.

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#Defensible Space  # Fire Safety  #Fire-Resistant Plants

This article appeared as “Defensible Space and Fire-Safe Gardening” in my “Farm & Garden” column in the July 2014 issue of the Poway Progress newspaper.





From my FARM & GARDEN column from the March-June 2000 issue of the Poway Progress newspaper

By Kathryn Hughes


     What fruit can match the delicious taste of juicy, sun ripened strawberries? The fruit brings a natural sweetness to strawberry shortcake, fruit salads, and jams.  Piled high in a pie shell, strawberries add beauty to the dessert table.

Spring is the time to begin planting for these mouth-watering red jewels of the garden, as everbearers planted now will produce crops in the summer and fall.  Plants that have been planted in late summer or fall will produce the following spring. There are many varieties of strawberry to choose from, making it possible to have fruit ripening over a long season.  Obtain plants that are certified virus-free.  Pinch off the earliest blossoms to encourage stronger plants.

Strawberries enjoy a sunny location with well-drained soil.  Planting can be done in rows  or raised mounds about 5-6 inches high, using furrow irrigation, or on flat ground with overhead watering.  They also do well as container plants.  Plant strawberries 14-18 inches apart, with the crown just above the soil level to prevent crown rot.  Roots should be no closer than 1/4 inch from the soil surface or they will dry out.

Most varieties produce offset plants on runners. Pinching the runners will produce fewer but larger berries on large plants.  Runners may be left to produce offset plants, filling in the garden space to 7-10 inches apart. Replace plants every three years, every two years for everbearers.

Strawberries need frequent deep soaking, especially during the bearing season. Mulch to keep down weeds and conserve moisture.     Feed at planting time and again after the first crop, as nitrogen is especially necessary.

I’ve only been bothered by snails, slugs and pillbugs in my strawberries. Snails and slugs can be deterred by hand picking, or with shallow containers of beer or yeast and water placed about 20 feet away from the garden to attract them. Pillbugs and can be encouraged to congregate on orange rinds and removed by hand. Cornmeal is hard for pillbugs to digest, and can be dusted around the plants to reduce the pillbug population.

Strawberries can also be attacked by spider mites and aphids, red stele (root rot), verticillium wilt, and yellows (a virus). If using chemicals, use only before the fruit has set.  Use netting to prevent theft from birds. Keep the plants clean of rotting fruit.

Protect strawberries from frost when temperatures drop in late fall or early winter with a four-inch cover of mulch such as loose straw or tree leaves.  Remove the mulch cover when growth resumes in spring. Usually most of the tree leaves decompose prior to the  growing season, but they last long enough to provide the needed protection during the winter.

Strawberry plants are an attractive addition to the garden with their white flowers and red fruit decorating the clumps of green.  They are sure to be enjoyed even before eating the tasty fruit.