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Plan Your Fire-smart Garden

Two key components to creating defensible space are planning and maintenance.  Most traditional residential landscapes include foundation plantings and large trees and shrubs near the house.  We are used to this look but there are better ways of organizing your landscape that may help protect your home when a wildfire is burning nearby.  Start by understanding the defensible space zones.  With the zones in mind, observe climate conditions which will inform your choice of plants and placement on the property.  When choosing plants, know its size at maturity and space in the garden appropriately.  Other conditions such as soil type, irrigation and use of noncombustible paths and hardscape materials help to interrupt the path of fire.

Defensible space and your garden

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 
    There are many strategies and products that can help harden your home against fire. Although this is not in the purview of the UC Marin Master Gardeners, we strongly encourage you to contact your local fire agency for advice and guidance about how to harden your home. In addition, we also recommend that you and everyone living in your home know your evacuation route and keep it cleared of vegetation. Finally, 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
    When a fire started by an ember engulfs a home, that burning home becomes the biggest risk to surrounding homes. Therefore, it is critical to work with your neighbors to create larger rings of defensible space in and throughout your broader community. If expense is a concern, start small. Do what you can. Work with your neighbors to seek help with labor and materials. Here are suggestions for working with your neighbors to create community-wide defensible space.
  • 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. An appropriately landscaped and maintained defensible space reduces the fire risk to structures and provide an area for fire fighters to protect your home. Defensible space also uses the judicious selection and placement of plantings as a strategy to decrease the spread of fire.
    Photo credit: FireSafe Marin
    Photo credit: FireSafe Marin

Defensible space zones

As you evaluate your property in the context of the three zones outlined below, consider the size, location, structure and condition of your plants. It is sometimes helpful to think of zones creating a bowl effect, with your home sitting in the middle of the bowl. In general, the goal is to have the lower plants closer to the house and the larger plants and trees further away from the home. The 0-5’ area immediately surrounding your home’s perimeter is recommended to be void of plants. From 5-30’ from your house the plants gradually increase in size, which begins to create the bowl effect. From 30’ and beyond, larger shrubs and trees create the tallest points of the landscape – that is, the rim of the bowl.   It also means leaving some 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. Finally, defensible space also means allowing vertical and horizontal space between shrubs and trees, especially on slopes.

Zone 0: 0-5 feet from house

Zone 0
The area immediately surrounding your home should be the most fire-resistant. It should only contain noncombustible materials such as concrete, brick, paving stones, decomposed granite or gravel mulch. The goal is to avoid home ignition from blowing embers. Plants against combustible siding or under a window present the greatest hazard since, if ignited, their flames can make direct contact with the siding and can cause vertical flame spread onto the house. In addition, flames can ignite surfaces behind siding if allowed to enter at vulnerable points such as close to the foundation.

  • nothing flammable
  • no shrubs or trees of any kind
  • no dead branches or vegetation of any kind
  • no roof or gutter litter
  • no branches within 10’ of chimney or roof
  • nothing combustible under deck
  • no plants against combustible siding, under eaves, or near windows (flames rise 2-3 the height of flammable surfaces)
  • no combustible mulch, fencing, furniture
  • nothing combustible attached to house, including wood gates, fences, arbors, and trellises
  • no firewood or other combustible materials stored in this area

Zone 1: 5-30 feet from house

The objective of this zone is to 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 in this zone can help separate planting areas while also simplifying maintenance. Walkways should be made of non-combustible materials such as gravel, brick, or decomposed granite.

Zone 1 plants
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 house.
  • Trees, if any, should be small and they should not accumulate or drop more dead material than can be consistently removed from the site.
  • Assure all plants are accessible for maintenance.
  • 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.
  • Check to be sure plants are healthy and green during fire season.
  • 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.

Mulch, hardscape, and other materials

  • To increase the surface area of fuel breaks, break up mulched areas with hardscape material such as gravel or stone.
  • Relocate wood piles outside this zone.
  • Relocate large gas and propane tanks outside this zone.
    mulch hardscape

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

The objective of this zone is to 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.

  • Larger shrubs and trees in this zone should be planted in widely spaced groups or “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.
  • Native plants with low water needs may be a good choice.
  • Wood mulch is acceptable in this zone. (See maintenance for details about mulch)
  • During a wildfire move anything burnable such as patio furniture or gas BBQ tanks 30 feet away from structures.

Special situations: dealing with slopes and built structures

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 build structures that add to a garden’s comfort and practicality. Homeowners are encouraged to assess any built structures as they would other combustible materials. In essence, if improperly located, any combustible built structure – that is, anything made of wood – is at risk of exacerbating a fire unless precautions are taken.

  • Wood trellises, gazebos, sheds, and other structures should not serve as a path for fire.
  • Construction materials and methods for these structures should be as fire-resistant as for homes.

Trellises, for example, can be made of steel, and roofs of gazebos and sheds should meet roofing standards for homes.

Reference Materials for further reading

Preparing Your Landscape: https://ucanr.edu/sites/fire/Wildfire_Preparation_-_Recovery/Landscaping/

Choosing and spacing plants

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 will save you time and money. 

Plants provide a myriad of benefits.

Among other attributes, plants are home to many insects, birds, and animals. They attract pollinators, sequester carbon, produce oxygen, help reduce storm water runoff, and control hillside erosion. Studies show they even help reduce stress! We encourage you to grow a garden that enhances your home and lifestyle.

What plants should you use?

All plants burn. When it comes to fire-smart landscaping, 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. Homeowners are encouraged to choose plants that require little water, are easy to maintain, that do not provide excessive quantities of debris, and that contribute to the ecological health of the surrounding area.

“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 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, waterwise, 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 and spacing plants

Healthy plants are more fire resistant than plants struggling to survive. Thoughtful and 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. In general, aim to choose plants 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

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.
  • Choose native trees that have adaptations 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.
  • Space trees so that at maturity their crowns are fifteen feet apart or more. The greater the spacing between trees, the less likely that fire will spread from one to another.
  • Avoid planting trees in rows or hedges, since this can provide an uninterrupted path for fire.
  • Try to select trees that shed minimal amounts of needles, leaves, fronds, dry bark and other debris.
  • Avoid trees that have a tendency to build up dead thatch inside or under a green surface layer.

Shrubs

  • Avoid planting shrubs in rows or hedges, since this can provide an uninterrupted path for fire. Discrete “islands” of plants 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.

island planting

Reference Materials for further reading:

Preparing Your Landscape: https://ucanr.edu/sites/fire/PrePost/Landscaping/

Sustainable and Fire Resistant Landscapes: http://ucanr.edu/sites/SAFELandscapes/Invasive_Plants_and_Wildland_Health/

Protecting California’s environment and economy from invasive plants:  https://www.cal-ipc.org

Near-Home Vegetation: https://ucanr.edu/sites/fire/PrePost/Building/Plants/

Fire-smart Home Garden Design Examples

Design

 


LEGEND

1 - Fruit tree

2 - Sculpture

3 - Native low water lawn alternative

4 - Lounge chairs

5 - Driveway with gravel strip with succulents (no irrigation)

6 - Decorative gravel, Idaho Fescue, succulent mix 

7 - Grasses planted on grid

8 - Meadow or grasses planted on grid

Landscape Design Templates

A consortium of Sonoma County organizations developed eight front yard landscape templates that demonstrate best practices for creating fire-smart, sustainable, water-wise landscapes. These design templates have generously been made available free of charge for anyone rebuilding after fire or interested in modifying an existing landscape.

View the free front yard landscape templates.

Although these templates were designed for residents of Sonoma, they are appropriate for Marin homeowners as well. The designs are ready-to-permit, in compliance with local and California State Model Water Efficient Landscape Ordinances, and scalable for landscapes up to 2,500 square feet. The eight front yard plans are available in two of each of the following styles:

  • Sonoma Native/Adaptive – an emphasis on native and fire safer plants
  • Sonoma Eco-Edible – a mix of edible and habitat plantings that maximize sustainability
  • Sonoma Contemporary – a modern, minimalistic and clean look that is easy to maintain
  • Sonoma Cottage – a Sonoma version of a cottage garden with natural materials and colorful plantings

The UC Marin Master Gardeners are grateful to the following groups for making these templates available:

  • UC Master Gardener Program of Sonoma County (UCMGSC)
  • The City of Santa Rosa
  • Santa Rosa Junior College (SRJC)
  • Sonoma County Water Agency (SCWA)
  • Habitat Corridor Project (HCP)
  • California Native Plant Society (CNPS) – Milo Baker Chapter

Similar groups in Marin County will be working on design templates specifically for Marin home gardens.