February 2023 | Utah State University
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Landscaping in the Utah Wildland-Urban Interface Jordan Goff, David Anderson, Jake Powell, Darren McAvoy
What Is the Wildland-Urban Interface?
The wildland-urban interface (WUI) is simply where human development mingles with wildland, or in other words, developed land next to undeveloped land. This area is at the highest risk for damage from wildfire. Much of the WUI in Utah is in the foothills above our city centers (Figure 1). As our communities continue to grow outward, the WUI is only expanding, putting more people at risk from wildfire.
Figure 3. The Three Zones of Defensible Space
Fire-Protective Landscaping Figure 1. The WUI Is Between Urban and Wildland
Why Does the Utah WUI Need Special Landscaping?
Because the WUI has such high wildfire risk, it is important for homes built there to have fire-protective landscaping. Also, because Utah is a desert state currently in a drought, low-water landscaping is important for all Utah landscapes, including the WUI. So, ideal landscaping for homes at the Utah WUI will be fire-protective and low-water (Figure 2). This will help protect from home loss due to wildfire and save precious water.
Defensible Space The first and most important principle of fire-protective landscaping is defensible space. The main idea of defensible space is to reduce the amount and continuity of flammable materials between the wildland and the home. A good defensible space has three zones (Figure 3), each with their own requirements. Zone 1: The Home and Zero Feet to 30 Feet Around the Home • The home exterior should be made of nonflammable materials like stucco, concrete, and asphalt shingles. • There should not be anything flammable next to, on, or within 5 feet of the house. This could include trees and shrubs against the house, stacked firewood, or pine needles on the roof. • Firewood and propane tanks should not be stored next to the house. • Zone 1 should be sparsely planted with low-growing plants.
Figure 2. Ideal WUI Landscapes Are FireProtective, Low-Water, and Have Good Comfort and Aesthetics
• Make sure to give plants in Zone 1 enough water so that they are healthy and don’t dry out.
Zone 2: Between 30 Feet to 100 Feet Away From the Home • Zone 2 should be kept relatively free of fuel, with few trees and shrubs. • Planting should be in sparse, small clumps, not in large patches. • Trees should have their lower branches removed so that fire cannot travel from lower vegetation into the trees. Space trees out with at least 20 feet between canopies to prevent fire from spreading between them. • Turfgrass, paved areas, and sparse planting areas are ideal for Zone 2. • If you have a propane tank, place it in Zone 2, and have a 10-foot area surrounding it with no flammable materials (including plants). • The important thing to remember about Zone 2 is that it is creating a firebreak between the wildland and the home. The goal is to break the continuity of fuel so that it stops or slows down fire moving from the wildland to the home.