April May 2018

18 colorad o nga.org LooseLeaf April/May 2018 CSU RESEARCH UPDATE By James E. Klett, Ph.D. CSU Professor & Extension Landscape Horticulturist Some Superior Woody Plants to Consider for 2018 Research continues at Colorado State University on evaluating new woody plants for Colorado and the Rocky Mountain region. Currently we have more than 1,200 different taxa of woody plants that we evaluate yearly for growth rate and habit, flower and fruit characteristics, landscape features, hardiness, foliage characteristics, and disease and insect resistance. The following seven woody plants performed extremely well during the 2017 growing season and should be considered more for use in Colorado landscapes, especially along the Front Range. Annual reports on the performance of each of these cultivars can be viewed at landscapeplants.agsci.colostate.edu. Acer truncatum X Acer platunoides  ‘JFS-KW202’ PP21838 – Crimson Sunset ® Maple This hybrid has more heat tolerance, and its growth habit is more upright and compact. The foliage color is deep purple during the growing season and maintaining a maroon to reddish bronze for fall color. It is hardy to zone 4, and reaches a mature height of about 30 to 35 feet and width of 20 to 25 feet. The glossy, heat-resistant foliage on this hybrid defies heat and humidity by maintaining its rich, deep purple color through the summer months. Carpinus betulus  ‘Frans Fontaine’ – Frans Fontaine Hornbeam This clone has a narrow, columnar shape that is maintained with maturity. It has dark green summer foliage that turns yellow in the fall. It is hardy to zone 5, and matures to about 20 to 25 feet in height and 10 to 15 feet in width. The current season’s growth curves inward toward the central leader. Carpinus caroliniana  ‘CCSQU’ PP11280 – Palisade ® American Hornbeam This clone forms an upright, oval canopy with ascending branches and good density. The bark turns a sinewy gray color on mature trees. The summer foliage is a good green with yellow-orange fall color. It is hardy to zone 5, and matures to a height of about 25 to 30 feet and width of 10 to 15 feet. This clone brings a uniform street tree appearance to an otherwise variable species. Tilia tomentosa  ‘Sterling’– Sterling Silver Linden This is a vigorously growing tree with a very neat and broad pyramidal shape. It has two-tone leaves, with dark green above and silver below that shimmer in the slightest breeze. The fall foliage color is yellow, and it is hardy to zone 5. It matures to about 40 feet in height and 30 feet in width. Thanks to the fuzzy (tomentose) texture of the leaves, they resist the feeding of insects and are more Japanese beetle resistant.