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There are 1.45 million ash trees in the Denver metro area, with 330,000 of them in the City and County of Denver. That means about 1 in every 6 trees in the Mile High City is an ash tree. In other words, there’s a 1 in 6 chance the tire swing you loved as a kid is hanging from an ash and a 1 in 6 chance an ash is shading your house and saving you money on utilities.

That’s where you come in.

  • There are no natural controls to halt the feast of the emerald ash borer (EAB), which is foreign to these parts. But EAB treatments, when properly administered by a licensed tree professional, are 90 percent effective.
  • The city will take care of its own — namely ash trees located on city property, including parks. Residents will be expected to do the same, taking responsibility for any ash trees on their personal property and in the adjacent public rights-of-way.
  • If you decide to replace your ash tree with one of these City Forester-approved trees – some of which you might even be able to get for free – you’ll help maintain the long-term stability of our urban canopy.

EAB infestation

How can you tell if your ash tree is infested by the EAB? Look for D-shaped exit holes, wavy trail lines, bark falling off the tree and Northern Flickers, a type of woodpecker that eats the EAB, and crown dieback, which is illustrated by dying branches and branch tips in the upper and outer portions near the top of the tree.

EAB identification

The EAB is small enough to fit on a penny, so you are unlikely to get a chance to examine one individually. But if you do, the adult EAB is identifiable by its dark, metallic-green color and coppery-red or purple abdomen, which can be seen under its wings.

EAB devastation

If seeing is believing, take a stroll through the once-thick forests in the 25 states and parts of Canada where millions of ash trees now rot. Property owners and forest product industry operators have lost billions of dollars to the EAB.

Learn how to determine if you have an ash tree.

Images courtesy Colorado State Forest Service, Bill McNee (Wisconsin Dept of Natural Resources, and Joseph O’Brien (USDA Forest Service,