Written by Diana McGinn, 2020 Apprentice Master Gardener

In recent years, we have all become more aware of the risk of wildfires impacting property and communities in the Western United States, including Colorado. If you live in an area “located in or near natural vegetation of grasslands, shrublands, foothills, or mountains” you live in the wildland-urban interface^[1], which fire experts say WILL burn at some point. Have you given any thought about how your landscaping choices could help reduce the risk of property damage or loss of your home? It does not mean that your yard has to be an oasis of rocks and pavers with scattered specimen plants. Though effective, for those of us that enjoy a variety of plants, their habitats, cooling ability, and the visual diversity they provide, a sea of rocks is less than inspiring!

The latest guidelines for minimizing the risk of wildfire damage to your property recommends beginning near the home and other structures (Zone 1) working outward. The area within 5 feet of structures (including decks, fences, sheds, etc.) should be dominated by inflammable materials. Foundation plantings should be avoided or limited to, at most, a few scattered plants, relatively short, and well-watered. Do not plant near windows, vents, or decks to reduce the likelihood of fire entering the building. If building exteriors are wood or at the top of a slope, extend this zone beyond 5 feet to increase effectiveness.^[2]

From 5 to 30 feet from structures (Zone 2), the goal is to provide less fuel for a wildfire approaching your property. For good defensible space consider smaller plant clusters separated by non-flammable mulches or irrigated grass versus large, dense plant masses. Using organic mulches such as bark, wood chips, pine needles, straw, or other combustibles in this zone is not recommended, since they would add to fire intensity. Having separation between planting areas reduces the potential for high intensity fire development that could generate sufficient radiant heat to ignite a nearby structure.

There are few hard-and-fast rules for landscaping in Zone 2 since each property will have different variables to evaluate (surrounding vegetation, topography, elevation, wind exposure, existing structures and their flammability, etc.), but when trying to sort through which guidelines may be most important for your landscape planning there are some general considerations:^[3]

• Except for species with a high resin content, most typical herbaceous landscape plants that you water to keep green and growing in the summer, will have a high moisture content and are very hard to ignite under most conditions and will not increase the rate of fire spread;
• Xeric herbaceous plants or shrubs that require less water may have a lower moisture content (except cacti and succulents), but if planted in smaller clusters away from structures they should also not increase fire behavior;
• Conifers (junipers, pines, spruces) are more resinous and flammable than deciduous species, which tend to have higher water content and are less flammable;
• Green, growing grasses have a high moisture content and are not very flammable. When grasses not managed as a lawn complete their growth for the year and dry out they can be very flammable and potentially hazardous until they green-up the next spring, especially during dry, windy conditions,. In Zone 2, it is recommended that these grasses be mowed to 4 inches in height when they begin to dry for the year.
• At lower elevations especially, tall annual weeds and cheatgrass (Bromus tectorum) can also contribute to fire spread and intensity when dry and should be mowed or treated (prior to seed production is even better!) in this Zone.
• For property in forested or shrubland environments, there are additional recommendations by forest type regarding ladder fuel reduction, tree spacing, or shrub treatments in referenced literature.

Beyond 30 feet from structures (Zone 3), the goal is mainly to keep wildfires on the ground. Mowing is not necessary, but depending on your surrounding vegetation and topography, actions may be needed to break up fuel continuity.

If you live in the wildland-urban interface, the ultimate goal is to safely live with the possibility of a wildfire occurring and increase the likelihood of your home surviving a wildfire, under dry, windy conditions and even if firefighters are not present to protect it. It’s worth doing!

^[1] 2021. The Home Ignition Zone, A guide to preparing your home for wildfire and creating defensible space. Colorado State Forest Service. 16p.

^[2] csfs.colostat.edu/wildfire-mitigation

^[3] CSU Extension Fact Sheets 6.303 and 6.305, Fire-Resistant Landscaping and Fire Wise Plant Materials