Rob MacDonald and James E. Klett
Department of Horticulture and Landscape Architecture
OBJECTIVE AND JUSTIFICATION OF THIS PROJECT: Plant introduction programs such as Plant Select ® have a goal of promoting and introducing superior woody plants to the public. Currently, little research data is collected in a manner that is both timely and representative of conditions in different Colorado regions. There is no existing multi-year, multi-site, systematic, coordinated woody plant evaluation program in Colorado. This project utilizes multiple research sites throughout the state to evaluate woody plants in order to present a more reliable and accurate pool of information regarding plant performance in this region. Each plant taxon will remain in the study at least three years. In addition, we are introducing new plants into the trial each year. The purpose of this study is to enhance the palette of woody plants available for Colorado landscapes, and to determine that these plants can be produced in quantities and in timeframes making them profitable to grow here. Nursery propagators, growers, university researchers, and plant brokers have all provided input in determining the list of plants which merit study. They are grown in a coordinated effort at research facilities and cooperating nurseries.
Selected trees and shrubs were grown in field trials at multiple sites throughout Colorado.
SIGNIFICANCE TO INDUSTRY: Information from this program will assist members of the Green Industry by targeting woody plants which merit further study. Again, industry representatives and university researchers were directly involved in composing this list. With the information gained from this research, Plant Select® can work hand-in-hand with local growers to assure that the species or cultivar is a superior plant worthy of promotion in Colorado. When this plant is promoted, the nursery industry will have an adequate, locally grown supply to meet anticipated demands.
Colorado State University continued work with woody plant evaluation throughout 2006. Working with Plant Select®, researchers and industry representatives maintain a listing of plants unused or underused in Colorado landscapes. These plants have multiple ornamental features, and seasons of interest. With the 2006 planting, over 25 species/cultivars will be growing in this trial. Goals for this project include broadening the local palette of plant choices as well as collecting data on production of these plants to assist local nurseries and growers in determining if they should add these plants to their product line. There are five co-operating sites, including three private sector nurseries, Boxelder Creek Nursery (primarily south of Hudson, CO); Harding’s (Calhan); and Little Valley (Brighton). In addition, two Colorado State University research sites, the Horticultural Research Center, Fort Collins, and Western Slope Research Center, Orchard Mesa, at Grand Junction, are participating. There are ten replications of each plant at each site, planted in a randomized block arrangement.
Rhus 'Autumn Amber' (on the left) and Rhus 'Gro Low' (on the right) show differences in growth habit.
The Plant Select® Woody Plant subcommittee is revising the master list due to lack of availability of some plants. Following is the list of plants introduced into the field trial in 2006: Acer monspessulanum (Montpellier maple), Juniperus scopulorum ‘Woodward’ (‘Woodward’ Rocky Mountain juniper), Larix decidua (European larch), Prunus serotina (Black cherry), Pyrus ussuriensis ‘Burgundy’ (‘Burgundy’ Ussurian pear), Quercus polymorpha (Monterrey oak, Net leaf white oak), and Quercus undulata (Wavy leaf oak). Two of the taxa, Quercus polymorpha, and Prunus serotina, were produced in Texas with some harsh growing conditions. Hopefully, this will translate into enhanced hardiness in our Colorado environments. As of this writing, most plants have shown high levels of survival, although European larch is showing higher levels of stress and mortality than other taxa. Both the Black cherry and the Burgundy Ussurian pear showed exceptional growth rates, overall.
In 2006, in addition to completing the cold-hardiness evaluation of Arizona cypress and adding the above-mentioned seven species/cultivars to the trial, researchers will conduct the final data collection on the first planting, spring of 2002. These plants will in some cases be harvested or removed in 2007. In some cases trees will either be moved or remain in test plots.
Planting will continue in 2007, with Plant Select® composing a list and obtaining selections. Two sets of plants, those introduced into the trial in fall, 2002 and spring, 2003, will complete their fifth growing season in the trial. As with the spring, 2002 planting, researchers will collect growth and performance data on these trees to determine if any merit introduction into Colorado landscapes with the Plant Select® designation.
Arizona cypress in the field.
Thanks to: Colorado Nursery Research and Education Foundation (CNREF) and Colorado Agricultural Experiment Station (AES) for partial financial support for this project. Partial in-kind donations of plant material are also appreciated form Fort Collins Wholesale Nursery and Bailey Nurseries Inc..
Heptacodium miconoides (Seven-son Flower)
Plants are being evaluated for fall color among many other attributes.
