tree and park bench icon

1 million

Number of ash trees in yards, parks and streets throughout Hennepin County

emerald ash borer icon

100 percent

Number of ash trees that are susceptible to emerald ash borer and will die unless treated

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15 miles

Most residents live within 15 miles of an infested ash tree.

View interactive map of infested ash tree locations

Trees provide many benefits

  • Protect air and water
  • Shade homes and help to conserve energy
  • Provide habitat
  • Cool our streets and cities
  • Make our communities healthier
  • Reduce stress levels


There are several varieties of ash trees in Hennepin County – green, white and black – and all are susceptible to emerald ash borer.

Look for the following characteristics to determine if your tree is an ash tree:

ash tree branches

Branches grow directly opposite from one another.

ash tree leaves

Compound leaves, or multiple leaves on one stalk joined to a branch. Leaves commonly have 5 to 9 leaflets.

ash tree bark

Bark with diamond-shaped pattern.

ash tree seeds

Seeds are oar-shaped samaras that typically hang in clusters.


Treatment with an insecticide is an option to preserve ash trees of high value.

arborist treating an ash tree

What you need to know

  • A healthy, mature ash tree may be worth saving. The tree should be at least 30 inches in circumference (or 10 inches in diameter) at chest height and of value to the property owner.
  • Ash trees within five miles of emerald ash borer infestation should be treated.
  • Preservation treatments must be administered by a certified arborist every two years in late spring. Cost is typically $100 to $200 per tree but varies depending on the tree's size.
  • Hennepin County recommends using a trunk injection of emamectin benzoate (commercial name Tree-age), which is an effective treatment option. It is not a neonicotinoid, which has been shown to negatively impact pollinators.


Any ash tree not being treated will eventually need to be removed and disposed. A dead tree should be removed before it becomes a hazard.

removing an infected ash tree

What you need to know

  • If you decide to proactively remove ash trees, remove them between October 1 and April 30 to avoid the season emerald ash borer is active and in flight.
  • Trees should be removed by a reliable and insured ISA-certified arborist. Find an ISA-certified arborist near you.
  • To help reduce your individual costs, work with your neighbors to hire a company to remove trees on multiple properties.
  • Dispose ash tree waste at yard waste sites within Hennepin County.


Trees provide numerous benefits including improving air and water quality, reducing soil erosion, increasing wildlife habitat, providing savings in heating and cooling, and improving health. So planting new trees in place of any you remove is a great idea.

replanting a tree

What you need to know

  • Be safe and check for underground utilities before digging in the ground. Call 811.
  • Select a variety of trees that are well-suited to your growing conditions. View a list of recommended tree species or contact your city forester for recommendations.
  • Plant the right tree in the right place to ensure trees will stay healthy and provide maximum benefits. Follow proper planting techniques.
  • Help your new tree survive by ensuring it gets enough water. Young trees need 10 gallons of water each week throughout the growing season.
  • Learn more about proper planting, watering, mulching, and staking in the National Forest Service tree owner’s manual (PDF 9MB).

This resource is part of Hennepin County’s effort to maintain a healthy tree canopy and increase awareness about the threat emerald ash borer poses to ash trees.