Photo: Nancy Klasky
BROOMFIELD, Colo. – Homeowners considering planting a tree this fall, take heed: According to a report just released by the Colorado State Forest Service (CSFS), the fastest-growing planted trees for Colorado’s Front Range communities appear to be cottonwood, catalpa, silver maple, blue spruce and white oak varietals. Hawthorn, piñon pine and hackberry are some of the slowest growers.
White ash varietals, including the highly popular “Autumn Purple” ash trees common to Front Range neighborhoods, also are fast-growing, but are no longer recommended for planting in Colorado due to the threat of being killed by the non-native pest emerald ash borer (EAB).
The report characterized the long-term growth of 19 common urban tree species grown on publicly maintained land in Westminster over a 24-year period, as tracked by the CSFS and City of Westminster. The average trunk-diameter growth rates of nearly 1,500 trees, which represents all those that survived the study period in fair to good condition, can be used by homeowners, landscape architects, designers/installers and tree care professionals to select trees for planting that will most quickly provide shade, aesthetics and other benefits after planting.
Keith Wood, CSFS community forestry program manager and lead study author, cautions that tree growth rates should not be the only factor consumers look for when buying trees at a local nursery.
“Factors like insect and disease susceptibility, hardiness in our harsh climate and soils, and shorter lifespan in some faster-growing species should also be considered when selecting the right tree,” he said. He warns that some fast-growing shade trees, including cottonwoods and silver maples, are prone to branch breakage in the state’s all-too-common late spring and early fall snows, while slower growers like hackberry and honeylocust can be excellent choices as they thrive in this area.
Wood says that another key consideration when selecting trees should always be the goal of seeking high tree diversity within a community, to make the urban forest more resilient to future insect and disease threats that target specific hosts. He recommends that potential tree buyers review the “Front Range Tree Recommendation List” offered by the Colorado Tree Coalition, which includes descriptions of trees suitable for the area and drawbacks to consider. The list, along with an ash tree replacement selection tool and species diversity calculator, is available at Colorado Tree Coalition website.
To see the full growth-rate study results for all 19 tree species, view Growth Rates of Common Urban Trees in Westminster, Colorado.