A Firewise landscape in Arizona may include native and non-native plants as well as a variety of mulch materials. The goal of Firewise landscaping is to prevent home ignitions by using plants and mulch to reduce the spread of fires near structures or other improvements (DeGomez et al. 2002). Appropriate plants for a particular area in Arizona vary due to the proximity to structures, the location within the landscape (such as elevation and slope), as well as temperature and moisture regimes (Deneke 2002a).
Mulches are defined as any material used on the soil surface for a variety of reasons. The application of mulches to the landscape may improve the aesthetics, reduce soil moisture evaporation rates, improve the soil nutrient content over time, reduce weed competition, moderate soil temperatures, and provide cover for dust abatement (Appleton and French 1995; Rose and Smith 1996). With a wide variety of mulches available on the market, specific mulches are selected for different aesthetic and economic reasons including “eye appeal, color, size, availability, maintenance, and price” (Steward et al. 2003). Those that have been most popular in Arizona are: organic materials such as bark, wood chips, grass clippings, or compost; inorganic materials such as decomposed granite, rocks, or gravel; and finally synthetic sheet mulches or ground cloth, which are typically topped with an organic or inorganic mulch to hold them in place, protect them from ripping, and to hide them from view.
The Healthy Forest Restoration Act of 2003 was the impetus for the development of Community Wildfire Protection Plans, which emphasizes fuel reduction to protect homes, properties and communities. As fuel reduction projects are being implemented across Arizona’s woodlands and forests, much of the resulting debris is chipped and either spread back onto the site or taken to another location to be burned or used as wood chip mulch. Little is known about the flammability of this form of mulch, however, so an experiment was devised to test the relative ignition rate of this wood chip debris as well as seven other commercially available mulches using three different ignition sources. The objective was to determine the best mulch alternatives for Arizona’s landscapes for their unique arid environments. The flammability of plants recommended for Firewise landscapes will not be addressed in this publication.