Plant trees to replace ash, increase diversity

Many Coloradans plant trees in the spring because it’s the best time of year to get new trees established. 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 good time to consider planting new trees to ultimately replace ash trees that may later succumb to emerald ash borer,” said Keith Wood, community forestry program manager for the Colorado State Forest Service.

EAB, a non-native pest responsible for the death of millions of ash trees and billions of dollars in costs in 25 states, was confirmed in the City of Boulder in 2013. Although EAB has not been confirmed in Colorado outside Boulder, one of the reasons the exotic pest is a concern for communities all over Colorado is that an estimated 15 percent or more of all urban and community trees in the state are ash.

Wood says that with EAB expected to kill many Colorado ash trees in the coming years – and because it takes decades for most planted trees to reach maturity – it makes sense for homeowners not only to assess the health of their ash trees, but to 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 10 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 in Colorado, and a list of recommended trees to plant along the Front Range. To see the full list, go to http://www.coloradotrees.org/find.php.

Read more in this issue of Colorado Green NOW:
Earth Day reminder: Green Strategies for Colorado Landscapes
Today is National Day of Service for Front Range volunteers
Planning a more sustainable urban forest
Is your office wasting money?