- Author: Birgitte Elbeck, UCCE Master Gardener
If your garden is on the coast, you might easily choose to bypass this article.
Please read the closing paragraph on Coastal wildfire concerns before moving on to another topic, you may find it useful.
Introduction:
To the extent that the Humboldt and Del Norte Master Gardeners have a slogan, it is ‘Right Plant Right Place.' Four little words to encompass all the considerations for predicting whether a plant will do well in a specific spot in your garden. Typically, these considerations center around your particular location's climate and microclimate, soil, water, amount of sun, and the maintenance that you will be able to give the plant. These considerations are fundamental for creating a healthy and enjoyable garden. However, with the advent of increased wildfire activity in California and around the world, additional constraints are needed in your garden landscape in order to increase the odds that your home will remain safe from wildfire. Satisfying all the constraints in a single season may feel too overwhelming, so you may want to initially pick some items to fix that you feel will make your specific situation safer. Home hardening efforts should always be considered alongside the Fire-wise enhancements to your garden, but this article will not cover those aspects.
Basic principles for creating a Fire-wise & sustainable landscape:
- Adhere to the evolving Defensible Space guidelines.
- Keep your garden's unique aspects in mind.
- Select all plants carefully and place them in locations that will give them adequate room to grow.
- Design for ease of maintenance.
- Communicate and cooperate with your neighbors.
- Do what is required by law. Scientific research on the new reality of wildfire is ongoing; use science to inform your decisions.
Defensible Space and placement of plants:
The premise for fire-wise landscaping is quite simple: change the garden and landscape around the home in order to protect the structure. However, the implementation can sometimes be tricky, often involving cooperation with neighbors, and it always requires maintenance and vigilance over time to remain effective. Talking to neighbors and coordinating within the immediate neighborhood should be an essential part of your efforts. Remember, by working together, you can create a safer environment for everyone in your community.
The concept of ‘defensible space' is a cornerstone of fire-wise landscaping, as promoted by CalFire and other fire-related agencies. It involves managing zones of varying levels of fuel reduction, with the most stringent reduction near the home, and considering the relative placement of landscape components. This approach outlines prudent spatial landscaping constraints, particularly in rural settings with ample space and trees. Its primary focus is on halting the path of fire toward your house and ensuring the safety of firefighters operating in your vicinity during a fire. In your garden design, it is advisable to think in terms of ‘islands' of plantings rather than continuous hedges or other plantings.
There are three zones to take into consideration.
- Zone 0 is the first 5 feet out from the house, focusing on intense fuel reduction to protect against ember attacks. Zone 0 is a recent addition, and you may still find websites, etc., that do not reference it. It was implemented after it became clear that an exceptionally large percentage of structure fires start from flying embers that get caught immediately next to a building. Such flying embers can come from a blaze that is a mile or more away, making it difficult to predict when and where embers will land.
- Zone 1 covers from 5 feet to 30 feet. The goal is to reduce fuel sources and includes removing all dead plants, leaves, and grass, pruning overhanging branches and flammable plants and shrubs near windows, allowing 10 feet between trees,
- Zone 2 from 30 feet to 100 feet. The goal of Zone 2 is to reduce fuel sources.
The illustration below shows the bands of zones. The defensible space rules are still evolving, and your best bet is to get updated information at Defensible Space | CAL FIRE.
For more information about defensible space https://readyforwildfire.org/prepare-for-wildfire/defensible-space/
Plant spacing of grasses, shrubs, and trees is key in slowing the spread of wildfires. Spacing varies depending on the slope of the land, plant and tree type, and size.
Wildfires travel at different speeds based on many factors, but it is generally true that fire moves up-slope at a fast pace. If your home has a slope down from it, then you will need to pay attention to the spacing of trees and other plants. The steeper the slope, the more generous the spacing needs to be. Note in the sketches below that if there are bushy ‘ladder fuels' under the trees, then the distance is not from one tree trunk to another, but instead from one ‘island' to another.
SLOPE & DISTANCE Between Plantings
Vertical spacing
- Trim branches at least 6 feet from the ground.
- Increase vertical space between shrubs and trees to prevent the fire from climbing. For example, a 5-foot shrub near a tree will need 15 feet of clearance to the tree's lowest limbs.
Horizontal spacing
- Is determined by the slope of the land.
- The steeper the slope, the greater the distance between plants/trees. See the illustration on the right.
Plant placement and maintenance are more important than plant attributes, and plant attributes are more important than specific plant species:
As you have seen, Defensible Space is focused on spatial considerations. The specific plants for your Fire-wise garden should be chosen based on their physical characteristics and on the amount of care that you plan to give them. Keeping up with irrigation, pruning, and leaf litter cleanup is essential, even with plants that are less fire prone. All plants can burn, regardless of how they are marketed!
Plant attributes: |
Comments: |
Does the plant contain a lot of waxes, oils, and resins? |
A plant with more waxes, oils, and resins will likely be more flammable and release more energy when it burns. (Conifers are generally high in resins.) |
What is the leaf moisture content? |
Leaves with higher moisture content are less flammable than drier leaves. (See more on succulents below.) |
Does the plant have an open-growth structure? |
A densely structured plant can capture embers and may be more likely to ignite. It will also be more likely to be easily ignited by a surface fire. (See the Crape Myrtle example below.) |
How fast does the plant grow? How tall will the plant grow? |
A plant that grows quickly may exceed growth expectations and require greater maintenance. Pruning, maintenance, and cleanup can have a greater impact on whether a plant ignites than does the type of plant it is. |
Does the plant shed bark, leaves, or needles?
|
A plant that sheds bark or branches is likely to need more regular maintenance-related cleanup to reduce fuel accumulations on the ground. (Example: Eucalypts) A plant that has a big leaf or needle drop will result in the need for more maintenance-related cleanup on the property, on the roof, and in rain gutters. |
Is the plant native to the area? |
Native plants, pollinator-friendly, or drought-tolerant plants can be good choices for those labeled qualities, but these features do not directly translate to fire resistance. |
Fire resistant plants.
Labeling any plant as fire-resistant is an oversimplification of a complex problem. There can also be confusion as to whether a plant is resistant (does not easily catch fire) or resilient (has the ability to survive or has seeds that will survive). So, relying on lists of fire-safe plants is not the best thing to do. Below are just a couple of examples of plants that you may find on such lists, with some corresponding comments.
Crape myrtle (Lagerstromia indica)
These beautiful small trees (or bushes) tend to develop suckers that, if not removed, can form a dense cluster. The crowns can become dense, so they require ongoing pruning and thinning. Also, some gardeners like them positioned as hedges, which could cause a fire to travel quickly along the length of the hedge.
Manzanita (Arctostaphylos spp)
These native plants range from low, spreading plants to large bushes. They have a lot of appeal both because of their flowers and their striking bark. In a garden they are sometimes planted under larger trees, thereby creating a ‘ladder' for a fire to reach the crown of a tree above it. If a manzanita burns, it burns hot, but in the wild they have an amazing ability to re-sprout from the root, making them resilient.
Succulents (numerous genera)
In zone 0, succulents may be a choice for those of us who are not excited about switching to hardscape around the house. There are many varieties of succulents that hug the ground and contain a lot of water in their fleshy leaves. It has been suggested, though the jury is still out on this, that such plants, when well maintained, may actually help keep swirling embers from reaching the base of your house. Sonoma County's Master Gardeners have a great page on succulents: https://sonomamg.ucanr.edu/Recommended_Plants_for_Sonoma_County/Succulents
Coastal wildfire concerns:
The counties of Humboldt and Del Norte are blessed with a long, beautiful coastline with a cool and moist climate, and most of our population lives near the ocean. It is the hotter, forested inland areas that have seen the bulk of the wildfires. However, the coastal communities should not be complacent, as indicated by this snippet (Chapter 14 Wildfire Hum Co-LHMP (ca.gov)):
Despite the generally damp climate prevailing in these forests, studies have suggested a historical fire return interval of 50 to 100 years in the northern part of [Humboldt County] and 12 to 50 years in the south. Several of the more destructive historical fires occurred on the coast around the Trinidad area, including the 7,432-acre Luffenholz Fire of 1908, the 17,527-acre A-Line Fire of 1936, and a 15,000-acre unnamed fire near Patrick's Point in 1945.
Resources:
Much of this article is based on a document from Humboldt/Del Norte's own Yana Valachovic, Forest Advisor for the University of California Cooperative Extension and Humboldt – Del Norte County Advisor and colleagues: Reducing the Vulnerability of Buildings to Wildfire: Vegetation and Landscaping Guidance _UC ANR publication 8695.
CalFire
Defensible Space https://www.fire.ca.gov/dspace and https://readyforwildfire.org/prepare-for-wildfire/defensible-space/
The devastating Camp Fire of 2018, along with the numerous fires North State residents have experienced since then, have led many of us to focus on creating a defensible fire-resistant landscape around our homes. As noted in this column last Friday, the key to establishing defensible space is to utilize plants that are fire resistant and judiciously space them both horizontally and vertically.
Shrubs that are fire resistant include ceanothus, butterfly bush, spirea, rose of Sharon, Oregon grape, lilac, mock orange, potentilla, forsythia, cotoneaster, island bush poppy, currants, camellia, azalea, monkey flower and viburnum. Aloe and other succulents are generally considered fire-resistant but avoid succulents such as ice plant that produce mats of flammable dry material.
Choose deciduous trees such as maples, oaks, sweet gum (liquidambar), locust, redbud, dogwood, ash, toyon, and smoke tree. Citrus and deciduous fruit trees such as cherry, peach and plum are fire resistant. Although most conifers are highly flammable, redwoods are the exception to the rule and are a desirable tree in a firewise landscape.
Highly flammable plants often have an excess of fine dry or dead material and contain volatile waxes, terpenes, or oils. Their sap is gummy or resinous and aromatic. They may have loose, papery bark as well. Examples of flammable plants are sagebrush, conifers (cedar, pine, juniper, fir, Italian cypress), broom, rosemary, eucalyptus, palms, feather and fountain grasses and dry annual grasses. These plants should be avoided when planning a firewise landscape; if they already exist in a landscape, consideration should be given to removing them.
For more information on creating fire resistant landscapes, see the Firewise Landscaping section of our website. For more information on creating fire resistant landscapes, attend our Firewise Gardening workshop on May 2, 2024, part of the Master Gardeners' current Spring Workshop Series. For information about all the workshops, and to register, visit our website. All workshops are free, but registration is required. There is plenty to choose from workshop-wise this month and next: In addition to Firewise Gardening, topics covered include composting, native bees, pest management, weed identification, and California native plants.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
It's springtime, and many of us are adding new plants to our gardens. That means it is also a good time to review the principles of creating defensible space around our homes.
The key to establishing defensible space is to utilize plants that are fire resistant and judiciously space them both horizontally and vertically. Increasing the space between plants limits the ability of fire to spread. As a rule of thumb, Cal Fire recommends that on flat ground the space from the edge of one shrub to the edge of the next be twice the height of the shrub. For example, if shrubs are two feet tall, they should be spaced four feet apart. If the shrubs are growing on a moderate slope the space between them should be four times the height of the shrub. The space between trees should be 10 feet from canopy to canopy and increase to 20 feet on a moderate slope.
If a fire reaches the crown of a tree, its heat intensity increases and this can increase the combustibility of surrounding vegetation. Low tree branches create fuel ladders that allow fires to climb into a tree. To prevent fires from ‘crowning,' these ladder fuels must be eliminated. Cal Fire recommends that the lower branches of a mature tree should be pruned to create a clearance of three times the height of the shrubs beneath it. For example if a shrub is four feet tall, the tree should be pruned so that there is 12 feet of clearance between the top of the shrub and the lowest branches of the tree. For younger trees, the lower one-third of branches should be removed.
Applying mulch is a good strategy for conserving soil water, reducing weeds and preventing erosion. Normally, materials such as wood chips, shredded bark, leaves or straw are used as mulches because these organic materials have the added benefit of enriching the soil and improving its water-holding capacity. However, organic materials burn, so within the five feet closest to a home, it is recommended that non-combustible mulches of rock, gravel, pavers or broken concrete be used instead of traditional organic materials.
When planning a firewise landscape, the contribution of hardscape features should not be overlooked. Decomposed granite, cement, asphalt or gravel pathways and driveways make effective firebreaks. Structures such as patios and masonry walls and water features like pools, ponds, and streams will also impede the advance of a fire.
Before moving beyond the 30-foot home defense zone, mention should be made of items that do not belong too close to a home. Most propane tanks should be located a minimum of 10 feet from any structure, and woodpiles should be at least 30 feet away. A cord of seasoned firewood contains the energy equivalent of approximately 174 gallons of gasoline! Would you store that much gasoline on your porch? Also, flammable liquids such as gasoline, paint thinner, and turpentine should be properly stored away from ignition sources and combustibles.
If organic mulches are used in the reduced-fuel zone, a 2008 study showed that a mulch of composted wood chips spread two to three inches deep showed the slowest fire-spread rate of the eight mulches tested. A potential disadvantage of wood chip mulches is that they tend to smolder and can be difficult to extinguish. In general, fine, stringy mulches such as shredded bark burn more rapidly than larger chunks.
Establishing defensible space can be summarized by the following three R's: 1) Remove dead and dying plant material; 2) Reduce the density of vegetation and ladder fuels; 3) Replace hazardous vegetation with less flammable, well-irrigated fire resistant plants.
Further information on fire safety for homeowners can be found on the Cal Fire website at Home - Ready for Wildfire. And for property owners who are considering landscaping from scratch, the Sonoma-Marin Saving Water Partnership has developed eight fire-rebuild landscape design plans that are well worth considering (Water Smart Landscape Design Templates - Sonoma- Marin Saving Water Partnership).
For more information on creating fire resistant landscapes, attend our Firewise Gardening workshop on May 2, part of the Master Gardeners' 2024 Spring Workshop Series. For information about all the workshops, and to register, visit our website. All workshops are free, but registration is required.
Why not buy some plants for your fire-resistant landscape at the Master Gardeners' Plant Sale on Saturday, May 18, 2024? The sale will be held at our Demonstration Garden at Patrick Ranch, 10381 Midway, between Chico and Durham, from 9 am till noon. For more information, and a partial list of plants, see our Plant Sale webpage.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
Even when homeowners have created a defensible space, the job of protecting their home from fire is never done. There will always be ongoing and annual jobs to do. Additionally, there are special tasks that will need to be completed every few years or on an as needed basis.
A key ongoing yard maintenance goal is to keep plants green and lush, especially within the 30 feet closest to the home (the “home ignition zone”). Of course this means regular watering, which can be time consuming, but employing a drip irrigation system on a timer largely eliminates that concern. Using appropriate native plants should cut down on the overall need for watering as well.
The ground in the inner 30 feet around a home should also be kept free of leaves, pine needles, weeds and other ground fuels. Dead plants and/or tree branches should be immediately removed, as should any tree branches overhanging the roof. Tree branches should also be kept at least 10 feet away from a chimney. Vines growing on trees, shrubs, or fences can act as fire ladders and should be removed. Roofs and gutters should be kept free of leaves, needles and twigs. Gutter covers can reduce, if not eliminate, fuel build-up in this area.
If raised decks or porches are present, prevent combustible materials from accumulating in the areas beneath them. A preferable alternative to continually raking under decks and porches is to screen or enclose them with fire-resistant materials. If screening is used, the mesh should be no greater than one-quarter-inch. Flammable materials should be cleared from decks. This includes not only natural materials like leaves and needles, but items such as brooms and stacked wood.
Annually, before fire season starts, grasses and weeds should be mowed to a height of about three to four inches for at least 30 feet around homes and other structures. Grasses and weeds should be maintained at this height throughout the fire season. In fact, ground fuels should be kept at a minimum throughout the defensible space. As an alternative to mowing, string trimmers are a safer option for vegetation removal. To reduce the risk of fire due to mowing, make sure your equipment is properly maintained, mow before 10 a.m. and never mow on a hot or windy day.
Vegetation throughout the defensible space should be pruned for proper spacing, both vertically and horizontally, at least once per year. Cal Fire recommends that the lower branches of a mature tree be pruned to create a clearance of three times the height of the shrubs beneath it, while the distance between shrubs should be at least twice the height of the shrubs. In addition to maintaining proper spacing, pruning also makes plants more fire resistant. Cutting back woody perennials encourages less flammable new growth and thinning overgrown shrubs reduces their fuel load. Avoid topping landscape trees. Topping not only increases the fire hazard by encouraging excessive branching, but it is not healthy for trees.
Woodpiles should be located at least 30 feet from a home and should have at least 10 feet of cleared space around them. Covering a woodpile, or storing wood in a fire-resistant structure such as a metal shed, lowers the odds of the pile igniting during a wildfire. In addition, miscellaneous combustible materials including construction debris and brush piles should be removed from your yard as quickly as possible.
To aid firefighters, be sure your address is clearly posted so that it is easily visible from the street, especially at night. Also, be certain firefighters have easy access to water sources in your yard and, if possible, clearly mark those water sources. Fires often lead to power outages, so if you are on a well, it would be prudent to have an emergency generator to operate the pump if the power does fail.
Cal Fire has developed a “Homeowners Checklist” that describes how to make your home fire safe. It is an excellent, easy-to-use, comprehensive guide for homeowners. It is highly recommended. For more information on creating fire-resistant landscapes, see the Firewise Landscape section of the UC Master Gardeners of Butte County website. Other helpful sources include Yard Maintenance by UC Master Gardeners of Sonoma County and defensible space tips by the Butte County Fire Safe Council.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu (preferred) or call (530) 538-7201.
The devastating Camp Fire of 2018, along with the numerous fires North State residents have experienced since then, have led many of us to focus on creating a defensible fire-resistant landscape around our homes. As noted in this column last Friday, the key to establishing defensible space is to utilize plants that are fire resistant and judiciously space them both horizontally and vertically.
Shrubs that are fire resistant include ceanothus, butterfly bush, spirea, rose of Sharon, Oregon grape, lilac, mock orange, potentilla, forsythia, cotoneaster, island bush poppy, currants, camellia, azalea, monkey flower and viburnum. Aloe and other succulents are generally considered fire-resistant but avoid succulents such as ice plant that produce mats of flammable dry material.
Highly flammable plants often have an excess of fine dry or dead material and contain volatile waxes, terpenes, or oils. Their sap is gummy or resinous and aromatic. They may have loose, papery bark as well. Examples of flammable plants are sagebrush, conifers (cedar, pine, juniper, fir, Italian cypress), broom, rosemary, eucalyptus, palms, feather and fountain grasses and dry annual grasses. These plants should be avoided when planning a firewise landscape; if they already exist in a landscape, consideration should be given to removing them.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu (preferred) or call (530) 538-7201.