Perhaps there’s no time of year when Boiseans appreciate the city’s trees more than in the summer, when temperatures soar into the triple digits and shade is prized.
There are 45,000 to 50,000 trees in city parks and public rights-of-way — that includes those on the Downtown Boise sidewalks, in medians and the like. There are possibly several times that number on private property.
But most of the trees in the City of Trees aren’t native to the high desert. Officials are working to build up Boise’s tree canopy, or the percentage of the city shaded by trees, and they are encouraging Boiseans to help by planting more trees in their yards and by lending a hand with public projects.
Advocates of urban forests cite the benefits of trees in filtering pollutants from the air, reducing stormwater runoff, providing habitat for wildlife and increasing property values. Trees planted strategically around homes can reduce energy costs by 25 percent, according to the U.S. Department of Energy.
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“They aren’t just meant to stand there and be pretty — we’re glad they are. But they do a lot of heavy lifting,” said Boise City Forester Brian Jorgenson, who is in charge of the city’s 12-person Community Forestry Unit.
More shade, please
Cities around the country have set goals for their urban tree canopy. The cities of Phoenix and Tacoma, for instance, both aim to double their canopies by 2030, targeting 25 percent to 30 percent coverage.
Twenty years ago, the 140-year-old nonprofit conservation organization American Forests recommended that cities strive for 40 percent canopy. But they’ve since revised that due to the many variables affecting cities, including climate, and now say that 15 percent is a realistic baseline target for desert cities.
Boise has a 16 percent tree canopy cover, though there are parts of town that are significantly higher. The North End has a 34 percent canopy and Harrison Boulevard has a 41 percent canopy.
Boise’s Community Forestry Strategic Management Plan aims to grow the city’s canopy to as much as 25 percent by 2025.
“Increased canopy is just simply better for Boise,” said Jorgenson, who believes there are sufficient water resources to support that growth. “Cleaner air, energy savings, [higher] property values. Compare the North End’s canopy with others. It’s something that helps make Boise a better place to live.”
But the city can’t do it alone.
“We need people to plant more trees to get to 20 percent,” Jorgenson said.
Tree planting, maintenance programs
City forestry workers team up with community volunteers to plant trees in public rights-of-way every April as part of ReLeaf Boise. The NeighborWoods has provided free trees to property owners who agree to plant them 5 to 10 feet from sidewalks or streets.
The city also partners with Idaho Power on the Shade Tree Project, which provides free trees to Boise residents and across Ada, Elmore, Owyhee and Canyon counties. The project has distributed 7,500 trees since 2013.
“People love the program,” said Patti Best, who manages the Shade Tree Project. “They really understand the value of a tree. They understand it intuitively, that the tree is going to cool their house in the summer.”
Boisean Josh Buck, who lives in Southeast Boise, hasn’t heard of any of these initiatives, but his family planted six trees in their backyard this year: two different apples, a peach, a nectarine, a cherry and an oak.
“We wanted fruit-bearing trees for the kids and us but also to give some shade in the backyard,” Buck said. “We have no shade, and it really gets hot back there.”
The oak tree was one grown from an acorn his son found in Julia Davis Park. It was started at his father-in-law’s house a couple of years ago and was transplanted on the west side of their house this spring. The west side is recommended by experts to maximize cooling of buildings in summer, reducing energy costs.
“In 10 to 15 years from now, it will be nice and big and beautiful,” Buck said.
The forestry unit operates a nursery, the Laura Moore Cunningham Arboretum near Kristin Armstrong Municipal Park in the city’s East End. The roughly 5-acre site, donated to the city after Cunningham’s death in 1963, currently has 600 to 700 trees (about 30 different species), said Ryan Rodgers, nursery specialist.
Rodgers said the nursery gives staff more control over the quality of what they plant. Trees typically grow four or five years at the nursery before being replanted elsewhere.
Those who need help in deciding what types of trees to plant can consult the city’s online tree selection guide, which was authored by Jorgenson. The guide is broken into five sections: small trees, medium shade trees, large shade trees, conifers and species prohibited in public rights-of-way.
Helping Downtown trees
The concrete landscape of cities is a harsh environment for trees, magnifying the summer’s heat and compacting soil.
Jorgenson said Mayor Dave Bieter asked him find out what, if anything, could be done to improve the health, size and longevity of the trees Downtown.
Toward that end, the city has begun planting trees in Silva Cells, which are crate-like systems that are built under sidewalks. They aim to prevent compacting of the soil, allowing tree roots to grow and breathe.
Trees along 6th Street near City Hall were planted in Silva Cells, and so were the trees planted as part of the renovation at The Grove Plaza. Jorgenson said they’re hopeful the Silva Cells will double or even triple the life of trees Downtown.
They used to feel lucky if a tree survived a decade, and now they’re hoping to see them live 25 to 30 years.
“The city’s forest is part of the infrastructure. It serves a function every day,” Jorgenson said. “It’s green infrastructure. It keeps the air clean. It diverts stormwater. It saves energy.”
Have a question, concern or want mulch?
Boise Community Forestry is at 4649 W. Dorman St. in Boise. The office is open 7 a.m.-4:30 p.m. Monday to Friday, but call ahead because staff members are often out in the field. 608-7700. The emergency after-hours phone is 866-298-8766. The public can buy trees from the city nursery for planting in public rights-of-way. (City staff plant those.) The city also sells mulch at 4649 W. Dorman St. It’s $15 a cubic yard, and staff will load it into trucks, trash cans, totes and bags.
Some tree facts
▪ According to local lore, the black cottonwoods and willows along the Boise River stood out in the landscape to French-Canadian hunters passing through in 1833, leading them to exclaim, “Les bois! Les bois!” Boise is the French word for “wooded,” and some referred to the city as Wood River.
▪ Boise is part of the Treasure Valley Canopy Network, a public and private partnership that aims to expand the tree canopy across the Treasure Valley. The group’s website features canopy mapping tools.
▪ In any given year, Boise’s Community Forestry Unit, which has an annual budget of about $1 million, has to remove 75 to 125 trees due to disease, damage and/or hazard to the public. They also plant about 200 trees a year, so the inventory on public property is always growing, if slowly, Boise City Forester Brian Jorgenson said.
▪ Jorgenson’s staff is on call around the clock to remove downed trees or branches around the city (on public property). They divide the city into seven districts for pruning, and focus on a different district each year. They also field calls from residents concerned about specific trees.
“Occasionally, someone will call with a question about the health of a tree,” Jorgenson said. “If it’s a public tree, we’ll always go out and look at it.”
Flooding along the Boise River has meant more work this year in keeping the Greenbelt clear of trees and branches.
If they see or hear about a tree that’s got Dutch elm disease, they will remove it — or require it to be removed, if it’s on private property.
▪ Phoenix isn’t making very good progress toward its tree canopy goals — in fact, its publicly managed urban forest of about 94,000 trees is shrinking at an alarming rate, according to The Arizona Republic. About 1,000 trees on city-owned properties in Phoenix are lost annually to storms and other causes, and most aren’t replaced because the city nearly eliminated funding for tree replacement during the Great Recession, the newspaper reported May 27.