Oct. 14 2013 01:38 PM

Watching the news on television and seeing a house go up in flames tugs a little at your heartstrings. this year, fires have ravaged homes in three-fourths of the 50 states, reports the Los Angeles Times. as I’m writing this article, a wildfire is burning out of control near yosemite national Park. Worse yet, the flames could be rapidly closing in on homes and threatening nearby communities.

Because of people’s love of nature and their desire to live outside of the urban jungle, many homes are built in what’s called the wildland-urban interface, or WUI.

“It’s extremely risky. These areas are prone to wildfires due to the higher level of surrounding fire fuel,” says Joanne Drummond, executive director of the Fire Safe Council of Nevada County in Grass Valley, California. Without proper firewise landscapes surrounding them, homes built in the WUI can quickly meet with disaster.

For most of us, our homes are our most valuable investment. Losing property is catastrophic. However, many people don’t realize that living in mountainous or wild areas always brings with it an inherent danger.

How does a small, creeping brush or ground fire quickly become a raging, home-consuming inferno? Two words: “red snow.” That’s what fire experts call the flying, lightweight embers that float in the breeze. When they land on a fuel source, there’s trouble. Never underestimate the ability of flammable objects to become explosive projectiles in the midst of a firestorm.

But none of this needs to happen. You can drastically minimize the danger from fiery embers and save your clients from catastrophic damage to their property, and possibly loss of life to people and pets. You can do that by incorporating firewise practices into a residential landscape design. The landscape design alone can keep the home from burning.

Cut the fuel

So what is firewise landscaping? It’s all about fuel—decreasing, rearranging and, whenever possible, eliminating it. Fire can’t burn without fuel.

The first step is clearing and pruning the property of any obvious fuel source. Scan the property for dry leaves, fallen branches, and dead shrubbery.

Prune any dead tree limbs or branches, especially those that are hanging over structures. Raise the canopies of trees by removing lower limbs six to 15 feet from the ground. This helps keep fires from climbing trees, turning them into giant torches.

The next step is to create a plan.

Defensible space

Defensible space is the area that includes the home and its immediate surroundings. A minimum treatment area of 100 feet is recommended for homes and outbuildings on flat ground, and up to 200 feet or more on sloped sites. This is because fire behaves differently on slopes than it does on flat areas.

The rule of thumb is to increase fire resistance as you get closer to the home and structures. Trees should be kept furthest from the house, shrubs can be closer, and bedding plants and lawns may be the closest. There are three areas of defensible space, referred to as zones.

Zone 1 is the home or structure. In this zone, you’ll need to take steps to decrease and/or eliminate the ignition potential by creating a fuel-free area within three to five feet of the home’s exterior walls. “The first ten feet around the structure is considered the ‘home ignition zone,’” says Drummond. Nothing should be right next to the house that could possibly set it on fire.

Zone 2 is the landscape area, within 100 feet of the house. This is where perennials, ground covers and annuals should be planted in groups, along with individual trees and shrubs.

It’s best to surround these islands of vegetation with hardscapes, such as rock or brick retaining wall protection zones. Ground fires will not be able to advance when they encounter a hardscape element such as a rock wall, a sidewalk or a paver deck.

Don’t forget the mulch. It, too, can be a fuel source. Rubber mulch, for instance, is extremely flammable. Instead, choose pea gravel or other rock-based material.

Zone 3 is the area beyond the first 100 feet. This is where the property meets the forest. Here you’ll need to thin out native vegetation. Some landscape contractors will dig a trench to create a fire break between the forest and the start of the WUI area.

Now that you understand the rules of defensible space in a fireprone area, you can begin to design a successful firewise landscape plan. Keep in mind that you’ll have to approach the landscape differently in a WUI than in a normal residential area.

All plants are not created equal when it comes to fire resistance. Some burn much faster than others; generally, these are any species that contain an abundance of natural resins, oils and waxes. All of these fast burners will need to be removed.

Fire-resistant plants have the added benefit of being droughttolerant. They have high moisture content in their leaves, little or no seasonal accumulation of dead vegetation and are slow growing. Succulents are perhaps the ideal fire-resistant plants, due to their very high moisture content.

Familiarize yourself with the types of plants that are best, and worst, for a WUI landscape. Most states offer guidelines for help.

As you plant, keep growth potential in mind. Before you know it, a small bush can become a tall hedge that has grown right up under the eaves of a property, creating a direct fuel path to your client’s roof.

Placement of each plant is equally as important as plant type. “We look at it in terms of overall fuel loading. The arrangement of fuels is vitally important in terms of the way fire will behave in that vegetation,” says Drummond.

Every plant is its own vertical or horizontal ‘fire ladder.’ Drummond explains this concept. “Take a tree, for instance. A fire climbs up a tree and burns it like it’s going up a ladder.” A fire ladder also means anything that helps a fire jump to the next flammable object.

“You have two types of fire; ground fires, which burn along the ground, and crown fires, which burn across the tops of the trees,” says Dana Seelig, senior principal of Valley Crest Design Group in Santa Ana, California. A ground fire is easier to fight because it stays on the ground. “But what firefighters don’t want to happen is for shrubs with long fuel lengths or ladders to burn, and cause the tree canopies to ignite. Once this happens, fire can jump from tree to tree,” continues Seelig.

Fire also spreads along the ground from plant to plant, creating horizontal fire ladders. In the WUI, you need to increase the amount of space between plantings, thus increasing the amount of wind velocity needed to spread fire.

Tree or shrub height also needs to be kept in mind. A fire’s height can limit what fire fighters can do to protect a property, or keep them away altogether. For example, in Nevada, firefighters can’t be put on the ground when flame lengths are more than five feet. If you have a laddering effect on the property and the flame gets past those lengths, not only does it do more damage to the environment, but it restricts the tactics the firefighters can use.

You should have both horizontal and vertical separation. But this need not keep you from aesthetically framing your client’s home. You can use a ‘clumping’ technique, essentially creating islands of vegetation.

You can have some laddering in a clump, but if you do so, put it back 30 feet from the home. “Keep clumped vegetation far apart, at least 30 feet apart from each other, so that you’re creating ‘speed bumps’ which will slow the rate of fire spread and hopefully, allow firefighters to suppress it,” suggests Seelig.

Creating defensible space and correctly maintaining it will reduce the fuel. Should a fire happen anyway, these practices will reduce the flame length and the fire itself. “There have been many cases where defensible space has actually put a fire out,” added Seelig. “The fire just burns to an edge and goes out.”

Plant materials

Certain favorite species may not be suitable in a WUI; you can find substitutes that are just as aesthetically pleasing. Consider using native plants. “Native plants have evolved in the fire ecosystem,” says Drummond. “They thrive in the climate and soil indigenous to the area, so they’re going to be more successful and fire retardant in your landscape.”

Irrigation plays a vital role as well. The first 30 to 50 feet of defensible space should be well-irrigated at all times.

“Having a green zone immediately adjacent to the home will cause the fire to behave differently,” says Drummond. “It might smoke a little; it might singe the plants, but most of the time an area with a high moisture content won’t ignite.”


States and municipalities have plans, policies and regulations pertaining to WUI zones. You should familiarize yourself with these before you start putting in any landscape. These may include enforcement through landscaping ordinances, building codes, or covenants.

Some plants and trees may be restricted or even forbidden by law.

For example, the fire district in Southern California’s Big Bear Lake has what it calls “the 15-foot rule.” Because of the volatility of juniper, the rule says it cannot be planted within 15 feet of any structure.

Designing a firewise landscape with managed defensible space, vegetated with high-moisture, fire-resistant plants, strategically placed, dramatically reduces the threat that your client will lose his treasured wilderness home to wildfire.