Minneapolis and St. Paul finished removing public ash trees

Fifteen years later, they're all gone.

Completing work begun after the discovery of emerald ash borer beetles in Minnesota, the cities of Minneapolis and St. Paul have removed the last of the threatened ash trees on public property. Just about every ash left standing has been treated to protect it.

Emerald ash borers are insects that infest and kill ash trees, discovered in Minnesota in 2009. They have spread widely, threatening to lay waste to much of the state's estimated 1 billion ash trees, one of the largest concentrations in the nation. Most of them are located in forested lands, though tens of thousands were in the Twin Cities.

If left untreated, these infestations could devastate the entire ash canopy, said Rachel Morice, community forest project specialist for the Minnesota Department of Natural Resources.

So far the process has cost the two cities more than $50 million combined. St. Paul is turning its focus to publicly owned woodland properties and Minneapolis to ash trees on private lands.

Treatment and removal in St. Paul

In St. Paul, the last boulevard ash tree was removed June 4, marking the end of its Structured Removal Process, said Rachel Jongeward, St. Paul's urban forester supervisor. The city removed 26,947 trees in the past 15 years and is projected to have spent more than $36 million on emerald ash borer impacts by 2025.

There are still some ash trees in St. Paul. The city treats 112 ash trees in parks. Additionally, community members pay to treat 832 trees on public property.

Many ash trees also remain in St. Paul's wooded areas. The city is focusing on their removal to protect maintained spaces. Controlling already infested areas is crucial to slowing the spread of the ash borer, Jongeward said.

St. Paul does not condemn ash trees on private property unless they are a threat to neighboring areas, she said.

If an ash tree has not been treated yet, it is likely beyond recovery; Jongeward advises residents to get a licensed tree care company to assess its health.

Minneapolis' focus on private property trees

The Minneapolis Park and Recreation Board replaced approximately 40,000 public ash trees through its Ash Canopy Replacement Plan.

The city cut down infested trees, ground stumps and replanted a mix of new species. The plan cost taxpayers $1.2 million annually from 2014 until 2022, said Philip Potyondy, the Park Board's sustainable forestry coordinator.

Previously, entire city blocks in Minneapolis featured one tree species, and an infestation could devastate the neighborhood canopy. The Canopy Replacement Plan aimed to enhance tree resilience by planting a diverse mix of trees on each block. Minneapolis took its cues from eastern cities to develop the plan and now shares its experiences with other cities facing similar infestations, Potyondy said.

The Park Board is also condemning trees on private property. Ash trees are tagged for removal and information is left with the property owner. Homeowners are required to remove infected ash trees within 60 days. The cost of removing the tree is to be paid by the homeowner and can often cost thousands of dollars. The Park Board offers payment plans and financial hardship programs.

Outside the metro

While suburban communities are working to control the spread of the ash borer, cities in greater Minnesota are struggling, Morice said. Smaller rural communities often lack forestry departments or the funding needed to tackle the problem.

While efforts to control the invasive beetle may seem detrimental, Morice said Minnesota has experienced a slower spread than elsewhere.

"My hope is that in the fact that we've protected and we've slowed the spread, that we can have other trees growing in that canopy that are not ash," Morice said. "Hopefully those forests will have a little bit better of a chance to rebound."

The Minnesota Department of Natural Resources offers grant programs for emerald ash borer treatment and cities including Roseville and Rochester have signed up.

If you have an ash tree

Most Minnesota cities require property owners to manage ash trees on their land, whether through removal or treatment.

Ben Cooper, general manager of Rainbow Treecare, said a tree showing a large canopy decline probably needs to be removed. The cost of tree removal varies greatly depending on the tree's location and size and visible damage.

It is important for property owners to make a plan for their ash trees, he said.

"Don't wait for it to die because it just becomes a hazard and a lot more money out of your own pocket."

Grace Henrie is a University of Minnesota student on assignment with the Star Tribune.