Verona arborist outlines plan to grow canopy, phase out vulnerable ash trees

Jerry Halesman, the city’s certified arborist, told residents at an Arbor Day presentation that Verona manages about 4,800 public trees and is working to raise the city’s tree canopy from roughly 16% toward 25–30% through planting, maintenance and a new urban-forest strategic plan.

Halesman said the city plants roughly 300 trees a year, is treating ash trees to slow spread of the emerald ash borer and has launched a “heritage ash” program that will select about 50 high-quality ash trees to preserve while removing and replacing other ash trees over the next five to 10 years.

The plan matters, Halesman said, because trees deliver measurable annual benefits. “With that 16% we have almost $500,000 of annual benefits, and CO2 is sequestering worth about $300,000,” he said, adding that the city also counts roughly $100,000 a year in air-pollution benefits and about $90,000 a year in avoided stormwater runoff costs. He said the city also estimates nearly $10 million in stored carbon in existing trees.

Halesman described how Verona is responding to pests and diseases. The emerald ash borer (EAB) attacks ash trees’ vascular tissue; Verona has treated trees since about 2014–2015 and currently treats trees on a roughly semiannual cycle, he said. “We have started to implement, as of last year, a heritage ash program where we will be selecting 50, maybe more depending on funding, of the best quality ash trees in our city that will become heritage ash trees. The other ones will slowly be phased out over the next 5 to 10 years,” Halesman said. He said some treated trees will still be removed—he estimated the city will remove about 50 ash trees per year as it phases the population out.

The arborist walked through management priorities: tree health and safety (removing diseased or hazard trees), species diversity, correct pruning methods and planting the right species in the right places. He urged a diversity rule the city follows: “10% of species, 20% of genus, and 30% of family,” to avoid monocultures vulnerable to pests.

Halesman outlined steps the city has taken and plans to take: a DNR-funded urban-forestry grant that required a comprehensive urban-forest strategic plan, updates to the approved street-tree list, increased planting budgets to fill gaps on commercial lots, new in-house grinding equipment and purchases of electric tools and an electric utility truck to reduce emissions and noise.

He also described operational limits and site constraints the city faces—narrow terraces that limit rooting space, salt and compacted soils from construction, and conflicts with utilities—and said the department will trial suspended pavements, root barriers and other structural soil solutions on problem blocks. He recommended at least 10–15 feet of terrace width where possible to reduce sidewalk buckling and root damage.

On community engagement, Halesman said Parks & Forestry is partnering with the Chamber of Commerce, volunteers and Dane County on prairie and corridor restorations, and invited residents to volunteer events and an Arbor Day library planting scheduled to begin at 1:30 p.m. He also noted a May 18 volunteer hillside-restoration date connected to a ridge-reserve project.

The presentation closed with updates on parks and recreation projects that intersect forestry work—plantings at Century School Park, renovation projects at Epic Park and ongoing planning for a recreation center to occupy the old library site with programming planned to start as early as December—and an appeal for community collaboration on planting and stewardship.

Questions followed the presentation.