Colorado Multi-site Woody Plant Trials

Options for shade tree selection in Colorado are limited due to climate, soils and disease and insect issues.  Late and early frosts, dry winters with fluctuating temperatures and calcareous alkaline soils have traditionally limited the diversity of species which can successfully be grown in many parts of the state.  Increasingly limited and expensive water resources coupled with the dry climate of much of the state also make many mesic taxa less desirable.  At the same time, many commonly planted species have been affected by serious disease or insect issues such as; Dutch elm disease, thousand cankers disease and emerald ash borer.

In response to this the multi-site woody plant evaluation program in Colorado was started in 2002 at five different research and nursery sites throughout Colorado.  Since 2002, we have done twelve plantings evaluating a total of sixty-four (64) different taxa.  Trial plants are evaluated based on survival, growth, ornamental appeal and their potential to be invasive over a five year period.  In 2002, we started with five co-operating sites including three private sector nurseries, Boxelder Creek Nursery (south of Hudson, CO); Harding’s (Calhan); Little Valley (Brighton) and two CSU research sites, the Horticultural Research Center in Fort Collins (now ARDEC South) and Western Colorado Research Center – Orchard Mesa in Grand Junction.  Originally ten replications of each plant were planted in a randomized block arrangement.  A major hail storm in 2009 destroyed the planting at Boxelder Creek and we lost that site.  In 2015, we moved the Harding’s Nursery site to the Colorado Agricultural Leadership Foundation near Castle Rock, CO. 

In late 2008, we held an informational meeting with Plant Select® members and other interested personnel to re-evaluate the program and plan for the future of this research.  From this meeting, it was concluded that the research should continue but several changes were suggested.  Industry personnel at the trial sites will take more observational data throughout the growing season.  Also, standard nursery practices such as pruning will be done on all the trial plants to better evaluate the overall market potential.  Also, the number of replications was reduced from ten to eight.

Some of these woody plants have been recommended or introduced through the Plant Select® program including Acer tataricum ‘GarAnn’^PP15023 (Hotwings® Tatarian Maple); Arctostaphylos x coloradoensis (Mock Bearberry Manzanita); Arctostaphylos x coloradoensis (Panchito Manzanita); Heptacodium miconioides (Seven-son Flower) and Juniperus scopulorum ‘Woodward’ (Woodward Juniper).

Planting continues yearly.