Wildfire Defensible Space Pruning in Boise, ID

Wildfire defensible space pruning is tree work aimed at one thing: keeping fire on the ground and away from the house. Boise's foothills and the subdivisions along its edges back onto dry grass and sagebrush, and the city has designated wildland-urban interface areas with their own building and fire codes. The tree side of that job is pruning branches away from roofs, removing the low growth that lets a grass fire climb into a tree, spacing crowns, and taking out dead trees near the home.

Fire is not hypothetical here

Ada Fire Adapted, the program Boise Fire runs with its partners, lists the fires that shaped local planning. The Oregon Trail Fire on August 25, 2008 destroyed ten homes and damaged eleven in southeast Boise, and one resident died. A fire along Highway 16 on July 28, 2009 burned about 4,700 acres and destroyed four homes. The Table Rock Fire in late June 2016 burned more than 2,500 acres of foothills just above the city. The program also warns that embers can travel more than a mile, which is why homes that are not right next to open space still benefit.

What the guidance asks of trees

The Ready, Set, Go! guide that Ada Fire Adapted points homeowners to breaks the area around a house into zones. Closest to the home, it calls for pruning any branches touching or overhanging the roof back at least 10 feet and clearing dead leaves and needles from roofs and gutters. In the middle zone, it calls for removing ladder fuels so there is a gap between low plants and tree canopies. Farther out, it calls for removing ladder fuels up to 10 feet above the ground while keeping at least 75 percent of each tree's foliage, keeping at least 10 feet between tree tops, and removing dead trees and shrubs. We follow those numbers and adjust for each tree's health and form.

Doing it without ruining the trees

Limbing up a tree too hard, or thinning it to a few branches, trades a fire problem for a health problem. We raise the canopy gradually on young trees, cut at the branch collar, and favor removing a crowded or dead tree over butchering a healthy one. Dense evergreens that branch all the way to the ground right against a wall or deck are ladder fuels by definition, and are often better removed than pruned.

Free help worth using

Ada Fire Adapted offers free wildfire home safety evaluations by its mitigation team, and a free neighborhood chipping program in at-risk Boise neighborhoods, on Mondays for residents who sign up. The chipper takes woody limbs up to 12 inches thick, stacked in piles no bigger than 5 by 5 by 5 feet within five feet of the road. We can do the cutting and stack it for a chipping day, or chip and haul it ourselves. Call (208) 570-6500 to ask about the programs.