skip to Main Content

Denver’s Ash Trees Ready for Second Treatment

If you were out and about in Denver in 2016, you likely saw hundreds of ash trees wrapped in plastic that said, “Be A Smart Ash.” Denver Parks & Recreation’s Office of the City Forester treated public right-of-way ash trees adjacent to private properties throughout the city to prevent an Emerald Ash Borer (EAB) infestation. Although the treatment of ash trees by a tree care professional is 90% effective, treatment must be repeated every two to three years to remain successful. With this in mind, we will be treating these trees again.

Healthy ash trees that are 12 inches and larger in diameter at four feet off the ground were put on a list for potential treatment. From this list, a number of trees were randomly selected in each neighborhood to be treated in either 2016, 2017 or 2018.  Because trees require treatment every two to three years, we’re revisiting the 2016 trees now. Every ash tree scheduled to be treated was examined by a city arboreal inspector to determine if it was a good candidate for treatment.

EAB is a destructive pest that kills ash trees and poses safety and financial risks. However, this treatment, when done in advance, is more than 90% effective in preventing tree death.

photo courtesy of @watersa on Instagram

Risks of avoiding treatment Include:

  • Ash trees killed by EAB become very brittle and can break easily. Dead ash trees are dangerous to you and your neighbors and can be expensive to remove.
  • You are responsible for removing infested or dead EAB trees on and adjacent to your property, so treat your tree!
  • EAB has the potential to destroy Metro Denver’s 1.45 million ash trees – roughly 1/6 of Denver’s trees – significantly impacting our precious tree canopy.

Trees are critical for our overall quality of life. They produce oxygen, reduce smog, cool our neighborhoods and homes and increase our property values. Join our effort to save Denver’s ash trees by talking to your neighbors, friends and co-workers about EAB and encourage people to visit for more information. To see which ash trees are being treated and those that are candidates for future treatment, visit

Removing and Replacing Your Ash Tree

One of the four recommended treatment options for a tree infected with emerald ash borer (EAB) is to remove the tree and replace it with another species that can grow well in Colorado. Though the EAB has yet to be found and confirmed in the Denver Metro Area, the removal and replacement option is both cost-effective and convenient for homeowners.

Step one is removal of the ash tree and step two is replacement. While it sounds easy enough, hiring a tree professional will make this process significantly easier. When searching for a tree professional, this list of Certified Smart Ashes approved by the Denver City Forester is a great place to begin your search. There are many tree professionals that are licensed by the Office of the City Forester who can lend a hand.

We connected with the wise folks at Denver Parks & Rec to ask for their recommendations for tree replacements. We asked for suggestions for species that will easily thrive in our local climate when provided adequate care. Drumroll, please…

Smaller Trees | Less than 30-feet high

Amur Maackia – photo courtesy of Oakland Nurseries
Any redbud – photo courtesy of Arbor Day Foundation
John Pair maple – photo courtesy of Iowa City Landscaping
Peking lilac – photo courtesy of Forestfarm
Three-flower maple – photo courtesy of Heritage Seedlings

Shade Trees | 30-feet and taller

Espresso Kentucky coffeetree (without seeds) – photo courtesy of Your Garden Sanctuary
Prairie expedition elm – photo courtesy of Laidback Gardener
Tuliptree – photo courtesy of Tennessee Wholesale Nursery

Trees in the approved list are those which, given proper and consistent maintenance including supplemental irrigation, proper pruning, and avoidance of chemical contaminants, will be assets to Denver’s beautiful urban canopy. You can also explore the approved list in its entirety.