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Plan Your Fire-smart Landscape

 

PlantMaster
PlantMaster

Most traditional residential landscapes include foundation plantings and large trees and shrubs near the house. By observing your property and taking notes, you can spend time to think about how you can organize your landscape that may help protect your home when a wildfire is burning nearby. 

> Defensible space and your landscape
> Defensible space zones

> Choosing plants
> Spacing plants
> Special situations: dealing with slopes and built structures
> Fire-smart home landscape design examples

 

Defensible space and your landscape

Defensible space is the area surrounding your home where plants and other landscape elements are planned and maintained to decrease fire hazard. Defensible space also allows firefighters ample room to address embers and spot fires before they grow.

Start at the house and work out 
• Contact your local fire agency for advice and guidance about how to harden your home.
• Know your evacuation route and keep it cleared of vegetation.
• Make sure that your street is named or numbered, and a sign is visibly posted at each street intersection. Post visible street numbers for your house using at least 4-inch reflective numbers on a solid background.

Work with neighbors
• Burning homes are the biggest risk to surrounding homes.
• Critical: Work with your neighbors to create larger rings of defensible space in and throughout your broader community. If expense is a concern, start small, seek help with labor and materials.
• Suggestions for working with your neighbors to create community-wide defensible space.

 
Defensible space zones

These zones make up the 100 feet of defensible space required by law. Firesafe Marin
These zones make up the 100 feet of defensible space required by law. Firesafe Marin

To create defensible space, think about your garden in three zones. The concept of zoning, with increasing attention to fire safety in zones closer to the house, is central to fire-smart landscape design. The goal is to have the lower plants closer to the house and the larger plants and trees further away from the home.


ZONE 0: 0 to 5 feet from house

zone 0
OBJECTIVE: Create the most fire-resistant zone in the area immediately surrounding your home to avoid home ignition from blowing embers. Flames can ignite surfaces behind siding if allowed to enter at vulnerable points such as vents, or any gaps close to the foundation.

• Greatest hazards are plants against combustible siding and under or near a window or door. Flames rise 2 to 3 times the height of flammable surfaces
• Use only non-combustible materials such as concrete, brick, pavers, decomposed granite, or gravel mulch
• No shrubs or trees of any kind
• No dead branches or vegetation of any kind
• No live branches within 10 feet of chimney or roof
• Keep roofs or gutters litter-free
• Nothing combustible under decks
• Remove any combustible mulch, fencing, furniture, firewood, etc.
• Nothing combustible attached to house, including wood gates, fences, arbors, and trellises


ZONE 1:
 5 to 30 feet from house

OBJECTIVE: Reduce heat and movement of flame by creating a “lean and clean” environment.
• Zone 1 is a good place for a water feature, pool, or patio.
• Walkways here can help separate planting areas while also simplifying maintenance. Walkways should be made of non-combustible materials such as gravel, brick, or decomposed granite.

Plants
• Choose low, irrigated, non-woody plants such as vegetables, succulents, grasses, flowers, groundcover, or lawn in this zone. Plant low, well-irrigated plants closer to the house and larger shrubs and trees further away from the house.
• Prune to keep trees to a manageable size. Remove leaf litter, especially during hot dry months.
• Maintenance is key. Assure all plants are accessible for maintenance. Check to be sure plants are healthy and green during fire season.
• Provide vertical and horizontal space between shrubs and trees, especially on slopes, to avoid fire ladders (taller plants catching fire from nearby lower plants). Leave space between plant groupings (“islands”) to allow access for maintenance.
• Remove and replace struggling plants; healthy plants with a high moisture content are more difficult to ignite. Remove any dead trees, fallen branches, pine needles, leaves.

zone 1 display
Mulch, hardscape, and other materials
• Break up mulched areas with hardscape material such as gravel or stone.
• Relocate wood piles outside this zone.
• Keep or relocate large gas and propane tanks outside this zone.



ZONE 2: 30 to 100+ feet from house and out to property line

OBJECTIVE: Decrease the energy and speed of a fire by eliminating continuous, dense vegetation both vertically and horizontally. This is a transition zone on larger lots. It is the space between manicured gardens adjacent to the house and fringe areas abutting open space or between groups of houses surrounded by open space.

• Space out larger shrubs and trees in this zone into “islands” separated by areas of mulch or low groundcovers to break up and slow down the path of fire.
• Shrubs and trees should be well-spaced and pruned to eliminate fuel ladders, where fire can climb from a ground fire to an ember-producing crown fire.
• The taller the plants, the more widely they should be spaced.
• Maintain at least 10 feet of clearance between branches of adjoining trees or shrubs. Clumps of several trees may be treated as a single tree.
• Mow grass to a maximum height of 4 inches.
• Plants farthest from the house may not need to be irrigated, but they should be well maintained.
• California native plants with low water needs may be a good choice.
• Wood mulch is acceptable in this zone. 
• During a wildfire, move anything burnable such as patio furniture or gas BBQ tanks 30 feet away from structures.

 

Choosing and spacing plants

Piqsels.com
Piqsels.com

Through proper planning and ongoing maintenance, you can have both a beautiful and fire-smart landscape. Whether you want to modify an existing garden or create a new one, planning strategically will save you time and money. 

Plants provide a myriad of benefits. Plants are home to many insects, birds, and animals, attracting pollinators, sequestering carbon, producing oxygen, helping reduce storm water runoff, and controlling hillside erosion. Studies show they even help reduce stress! Grow a garden that enhances your home and lifestyle.

What plants should you use?

ALL PLANTS BURN. It is much more important to consider where a plant is situated and how it is maintained than to assume some plants are “better” than others. Unfortunately, there are no published fire-wise or fire-resistant plant lists that are science-based or peer reviewed.

“When creating a fire-smart landscape, we advise homeowners to design defensible space and maintain their landscapes according to UC Marin Master Gardener guidelines. For a new or renovated landscape, consider California native or other pollinator-friendly plants that require little water and are easy to maintain.  There are no published fire-wise or fire-resistant plant lists that are science-based or peer-reviewed.  Design and maintenance are more important than plant selection.”

- Steven Swain, UC Cooperative Extension Environmental Horticulture Advisor, for Marin and Sonoma Counties

Choose plants that meet your garden's cultural conditions and benefit the greater surroundings
The UC Marin Master Gardeners have created plant lists to help Marin homeowners select plants that are attractive, easy, water-wise, and pollinator-friendly. Some, but not all, are California native plants. If grown within the defensible space guidelines, any of these plants would be appropriate for Marin gardens.

Fire-smart guidelines for choosing plants
Healthy plants are more fire resistant than plants struggling to survive. Thoughtful and more informed plant selection and siting can reduce the threat of wildfire, cut maintenance costs, and help solve the growing problem of excess fuel loads not only on your property, but in your neighborhood and the broader community.

Plants
Choose those that:
• store water in leaves and stems
• do not produce excessive dead, dry, or fine debris
• maintain high moisture content with limited watering
• have low levels of volatile oils or resins
• require little maintenance
• contribute to the ecological health of the surrounding area
• See succulents and other low water plants

Trees
Choose trees that are:
• low in resin and sap content. Spend time researching the type of tree you would like using this tree searching tool,  then consult with your nursery to verify its resin and sap content.
• adapted to fire such as thick bark. These trees have a higher tolerance for fire and help restrict the growth of more volatile invasive and shrub species
• spaced so that at maturity their crowns are ten feet apart or more. 
• plants that shed minimal amounts of needles, leaves, fronds, dry bark and other debris
• Avoid planting trees in rows or hedges that provide an uninterrupted path for fire.
• Avoid trees that have a tendency to build up dead thatch inside or under a green surface layer.

Shrubs
• Avoid planting in rows or hedges, these can provide an uninterrupted path for fire.
• Aim for discrete “islands” of plants that are less likely to spread a fire. Ideally, island width should be no more than two times the height of shrubs and at least that distance apart.
• Avoid massing shrubs at the bases of trees or adjacent to structures, especially under eaves, overhangs, windows, or decks.

Fire-smart guidelines for spacing plants

Leave space between groups of plantings ("islands") to increase the surface area of fuel breaks and to assure all areas of the garden are accessible for maintenance.

Allow vertical and horizontal space between shrubs and trees, especially on slopes.

Space trees so that at maturity their crowns are 10 – 15 feet apart or more

Avoid planting trees in rows or hedges.

Remove tree branches 6 feet from the ground. If a plant is under a tree, allow extra space. Spacing on slopes increase as grade of slope increases.
 
Avoid massing shrubs at the base of trees or adjacent to structures, especially under eaves, overhangs, windows or decks.
 
See: Fire-smart home landscape design examples

 

Special situations: dealing with slopes and built structures

Landscaping and structure designed for fire safety Illustration:  EBMUD
Landscaping and structure designed for fire safety Illustration: EBMUD

Strategies for homes on hillsides

Fire tends to travel fastest uphill by preheating dried vegetation from below and making it easier to ignite. The steeper the slope, the faster a fire will spread. Narrow canyons and saddles act as chimneys that trap heat, channel wind, and create erratic fire behavior. Ridges are also fire-prone. Heavily vegetated slopes are particularly hazardous. If you live on a slope in a canyon or on a ridge, consider the following:

If there is horizontal space between the slope and your home, consider constructing a stone or concrete wall between your house and the most likely path of approaching fire to help deflect flames, heat, and burning embers away from the house. This is also a good place to install a lawn, pool, or patio of non-flammable materials such as concrete, brick, or stone.

Vegetation on slopes should be low in both height and volume, but it should not be completely eliminated because bare slopes may be subject to erosion and instability. Remove dead trees and shrubs, leaving the roots in place, if practical.

On slopes, plant widely-spaced, deep-rooted shrubs to help control erosion. Intersperse these plants with mulch or low-growing groundcovers.

Use retaining walls to reduce the steepness of slopes below the house. This may slow the spread of fire and also help to prevent erosion and slope instability.

Guidelines for built structures

Many landscapes contain built structures that add to a garden’s comfort and practicality. Assess all built structures as you would other combustible materials. Anything made of wood is at risk of exacerbating a fire unless precautions are taken. Risky structures include wood trellises, gazebos, and sheds.

Use fire-resistant construction materials and methods for these structures. Trellises, for example, can be made of steel, and roofs of gazebos and sheds should meet roofing standards for homes.