Many Coloradans plant trees in the spring because it’s the best time of year to get new trees established, and communities around the state will be hosting plantings this week to recognize Colorado’s Arbor Day, which this year falls on April 20. With the exotic, tree-killing emerald ash borer (EAB) establishing its presence in the state, there’s one more reason for planting in Colorado communities this year.

“Now is a great time to consider planting trees for any reason,” said Keith Wood, urban and community forestry manager for the Colorado State Forest Service. “One good reason is to ultimately replace ash trees that may later succumb to emerald ash borer.”

EAB, a non-native pest responsible for the death of millions of ash trees and billions of dollars in costs in more than thirty states, was confirmed in the City of Boulder in 2013. EAB has since spread and has now been detected in Longmont, Lafayette, Gunbarrel and Lyons. Wood says further spread is imminent in Colorado.
Although EAB has not yet been confirmed in Colorado outside Boulder County, one of the reasons the exotic pest is a concern for communities all over Colorado is that an estimated fifteen percent or more of all urban and community trees in the state are ash.

Wood says that with EAB expected to kill thousands of Colorado ash trees in the coming years, and because it takes decades for most planted trees to reach maturity, it makes sense for homeowners to not only assess the health of their ash trees this year, but to also plan for the possible loss of those trees down the road. He and other experts with the interagency Colorado EAB Response Team also want to make sure that Coloradans avoid planting any true ash species (genus Fraxinus), and that they remember to always plant for tree diversity on their properties and in their neighborhoods.

“No one species should comprise more than ten percent of the planted trees growing in any urban or community setting,” said Wood. “Whenever too many of the same type of tree are planted together, we are setting ourselves up for potential problems with insects and diseases.”

The Colorado Tree Coalition offers online descriptions of trees suitable to plant throughout Colorado, and also a list of recommended trees to plant along the Front Range. For more information, go to

More EAB information for homeowners is available at 

The Colorado State Forest Service (CSFS) provides professional forestry assistance, wildfire mitigation expertise and outreach and education to help landowners and communities achieve their forest management goals. The CSFS is a service and outreach agency of the Warner College of Natural Resources at Colorado State University and provides staffing for the Division of Forestry within the Colorado Department of Natural Resources. For more information, visit

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