FIRE SMART LANDSCAPING
A fire smart landscape isn’t necessarily the same thing as a well-maintained yard. This type of landscape uses fire-resistant plants that are strategically planted to resist the spread of fire to your home. Fire resistant plants are great in California because they are often drought tolerant, too.
The good news is you don’t need a lot of money to make your landscape fire smart. And you will find that a fire smart landscape can increase your property value and conserve water while beautifying your home.
Check your local nursery, landscape contractor or county’s UC Cooperative Extension service for advice on fire-resistant plants that are suited for your area.
Are there firesafe plants?
While some plants are marketed and described as “firesafe” or “fire resistant”, all plants will burn under the right conditions, regardless of how they are classified. The environment plants grow in and how it’s maintained will generally have more influence on the flammability of the plant than how it is characterized. For example, a plant with a good water supply could have a greater growth form and hold leaves longer, whereas a plant in a stressed or droughty situation may have stunted growth and accumulated dead materials. This can create a situation where the same species may be fire resistant in one environment and flammable in another.
Some plants, such as a lavender, may initially have lush growth and then several years later the growth may be woody and choked with dead materials. Other plants may develop a dead thatch layer, under a green surface, that is highly combustible. Regardless of plant type, ensure you follow the minimum vertical clearance model depicted below.
Be cautious of the claims of plants with a “firesafe” label. Bethke et. al (2016) reviewed 20 years of plant testing studies and determined that across the board there is “no consistent standardized plant flammability testing or criteria for rating”.
There are problems with definitions, types of testing, confusion between common and species names, consistency of plant care, and lack of testing across regions and climate areas. As a result, it is better to focus on characteristics of the desired plant and the location where the plant will be placed over a theoretical fire-resistant rating.
Characteristics and basic properties
Landscaping practices (or the pruning, maintenance, and cleanup) can have a greater impact on whether a plant ignites than does the type of plant it is. When bringing a fire-resistant framework to plant selection, consider whether the plant has a higher moisture content in the leaves (as these leaves will be less likely to ignite).
- Does the plant contain a lot of waxes, oils, and resins?
- Does the plant have an open-growth structure?
- How fast does the plant grow?
- How tall will the plant grow?
- Does the plant shed bark?
Depending on where you want to locate the plant, a plant with more waxes, oils, and resins is likely to be more flammable and release more heat energy when it burns. A densely structured plant can capture embers and may be more likely to ignite.
A plant that sheds bark or branches is likely to need more regular maintenance-related cleanup to reduce fuel accumulations at its base. A plant that has a big leaf or needle drop will result in the need for more maintenance-related cleanup to manage in your Defensible Space and on your roof or in your gutters.
A plant that grows quickly may exceed your expectations and challenge Defensible Space goals. Native plants, pollinator friendly, or drought-tolerant plants can be good choices for those labelled qualities, but they may or may not be any more fire-resistant than any other plant.
Placement is the most important criteria when it comes to fire-resistant plant selection. Keep in mind that vegetation that touches your home’s siding, is in front of windows, under eaves and vents, and/or under or near a deck will increase the likelihood that a home will be destroyed during a wildfire. Through the incorporation of best management practices within 0-5 feet of a structure, eliminating combustible vegetation and other combustible materials, reduces the potential that an ember can ignite a plant and reduces the potential for direct flame contact to your house to occur. By following the ideas in Zone One (0-30’ from the structure), where landscaping is separated into islands of vegetation and the continuity of plants is separated, the odds increase for home survival from direct flame exposure. Learn more about the different Defensible Space zones.
Additionally, all selected plants should be non-invasive and follow the minimum horizontal clearance model depicted below.
From a fire resilience perspective, vegetation management consists of good water management practices, appropriate fertilization, and a regular practice of plant pruning and cleanup. Regular watering, pruning, and cleanup increases plant health, making them more resistant to wildfire. Drip irrigation can be helpful as is mulch for water conservation. Unfortunately, combustible mulches near the home create an additional fire risk (Quarles and Smith, 2008). Eliminate combustible mulches within 0-5 feet from the home and recognize that from 5-30 feet, combustible mulch can burn and emit embers. Rock mulch will have greater fire resistance. Compost that is mixed into the earth around plants, has a lower combustibility or low combustible rating and are a better alternative to combustible mulches.
As any tree or plant ages, it sheds it’s leaves and older branches. To decrease the potential that fire will climb from the ground into a plant, remove lower branches, prune to create a more open structure, and clean up dead leaves and branches at the base. Monitor plant height and prune to reduce height and continuity to taller vegetation. Proper pruning techniques apply the same for trees and all woody plants.
Trees have many great qualities including their ability to absorb solar radiation and provide shade. Unfortunately, a tree that is overhanging a home can cause physical damage to the house from branches rubbing on the roof or walls, or more importantly from a fire perspective, trees can drop leaves and needles on the roof, in gutters, or on decks and surrounding landscape. From a fire perspective, it is recommended to remove trees or branches that overhang any roof or deck. A healthy and lush green tree canopy itself is not necessary immediately flammable or receptive to embers. To maintain the benefits of the shade tree while simultaneously increasing fire safety, move trees 5 feet away, prune the lower limbs, and eliminate vegetation, vines, and other dead fuels that would allow for fire to move from the ground to the crown of the tree. If a tree is diseased or showing signs of decline, consider its removal or replacement.
Quarles, S. and Smith E. 2008. The Combustibility of Landscape Mulches. University of Nevada Cooperative Education Publication SP-11-04. Reno, NV.
Bethke, J., Bell, C., Gonzales, J., Lima, L., Long, A., and MacDonald, C. 2016. UCCE San Diego. Research Literature Review of Plant Flammability Testing, Fire-Resistant Plant Lists and Relevance of a Plant Flammability Key for Ornamental Landscape Plants in the Western States. https://ucanr.edu/sites/SaratogaHort/files/235710.pdf