Article of the Month - May, 2008

Landscaping for Fire Prevention II: Choosing Fire Resistive Plant Materials and Other Landscaping Tips. by Yvonne C. Barkley

Many think that a truly defensible space is one that is devoid of all vegetation, ugly, and sterile. Who wants to looks at that? But, a fire resistive landscape does not have to be an ugly landscape. There are many ways to design and install a pleasing landscape that combines beauty with functionality and protection.

Choosing Fire Resistive Plants. Before discussing reducing fire hazard through plant material selection, remember – all plants will burn if there is enough heat and other conditions are right. The term “fire resistive” is used when referring to plants that are less flammable than others. The selection of fire resistive plants is usually far less important than how those plants and other landscape elements are configured in the landscape, and how those landscape materials are maintained.

Plant condition is as (or more) important as the species. Depending on plants’ growth form and access to water and nutrients, the same species may be fire-resistive in one environment and combustible in another. Summer irrigation may make the difference between an extremely flammable plant and one that will not burn readily.

Plants that ignite readily and burn intensely, known as pyrophytes or “fire-prone” plants, typically share certain characteristics. They:

• are water-stressed.

• usually accumulate fine, twiggy, dry, or dead material.

• have leaves and wood containing volatile waxes, fats, terpenes, or oils.

• are typically aromatic (crushed leaves have strong odors).

• have gummy, resinous sap with a strong odor.

• are commonly blade-leaf or needle-leaf evergreens.

• have stiff, leathery, small, or fine lacy leaves.

• may have pubescent (hair covered) leaves.

• may have loose or papery bark.

• are plants that flame (not smolder) when preheated and ignited with a match.

 “Fire-resistive” plants share the following characteristics. They:

• have a high moisture content in their leaves.

• are drought-tolerant.

• have little or no seasonal accumulation of dead vegetation.

• have a low volume of total vegetation.

• have non-resinous woody material.

• have an open, loose branching habit.

• are commonly slow growing.

When planning your landscape, use the characteristics of fire-resistive and pyrophytic plants along with site characteristics such as slope, aspect, hardiness zone, and amount of precipitation to choose plant materials suitable for your site.

Landscaping Tips. Here are some landscaping ideas that combine fire protection with pleasing and practical design elements.

Hardscape Elements

• Use hardscape features such as driveways, gravel, concrete, or paved walks as fire breaks. These firebreaks can be used to separate foundation plantings from the rest of the landscape, as well as provide safe and well-defined access to your property and home.

• Raised beds made from non-flammable materials such as rocks or bricks are another good way to create firebreaks between adjacent landscape areas. Even a short rock wall will provide an effective firebreak between a lawn and your home, or between fire protection zones.

• Use gravel mulch (versus bark) against any structures and under decks and porches and in areas adjacent to wooden stairs and fences. These areas should also be kept free of vegetation and debris.

• Clear excess plant materials from around propane tanks, which should be placed well away from your home. Also replace wooden fencing around tanks with non-flammable fencing materials such as chain link.

• Foundation plantings should be carefully selected and well maintained. Plants should be kept low, free of debris, and well watered.

• Large, paved patio areas not only provide effective firebreaks, but also increase your outdoor living space.

• Islands of vegetation in raised beds, surrounded by well-watered turf allows for a  beautiful, and fire resistive, landscape.

Water

• Your irrigation system could mean the difference between saving your home or not. Whether you have an installed, below ground system with pop-up sprinkler heads or a series of hoses and sprinklers, make sure they are well maintained. Plan on additional lengths of hose for placing sprinklers on roofs and decks in the event of an approaching wildfire. Also consider investing in a gas-powered generator to run the pump in your well in the event you loose power.

• A well-watered landscape is a fire resistant landscape. Use your water wisely and concentrate irrigation efforts in the areas immediate surrounding your home. If you are not able to water your lawn regularly, keep the turf short.

• Consider alterative water sources. Pools and ponds not only look great and provide recreational opportunities, but make excellent firebreaks and provide additional sources of water. If you install (or have) an on-site back-up source of water, make sure it is well marked and accessible to firefighters.

A well-designed and installed landscape can greatly increase the chances of your home and property from escaping destruction from wildfire. But fire protection doesn’t stop here!

Next - Part III of the Landscaping for Fire Prevention Series – Maintaining Your Fire Resistive Landscape.

For additional information and informative figures and photos, email the UI Extension Forestry office and request a copy of Protecting and Landscaping Homes on the Wildland Urban Interface. by Yvonne C. Barkley, Chris Schnepf, and Jack Cohen. Station Bulletin No. 67, January, 2005. Idaho Forest, Wildlife and Range Experiment Station, Moscow, ID.