| Abstract/Contents: | "The Shade and Flowering Tree Evaluation Project is sponsored by the Iowa Nurserymen's Research Corporation in cooperation with the Iowa State University Department of Horticulture. Forty-two selections of shade and ornamental trees were planted at the ISU Horticulture Research Station in 1986. Because of space constraints and poor drainage at the original site, a new evaluation site was established just east of the turfgrass research plots in the fall of 1990. Trees planted in 1990 include: Acer negundo 'Sensation' (Sensation Box Elder) - Three trees were originally planted and all failed to survive the winter of 1990-91. Acer platanoides 'Lamis' (Crystal Norway Maple) - A Bailey Nursery selection made in Oregon by Max Lamis. This maple is expected to grow 50 to 60 ft tall and is noted for its vigorus, straight trunk. It reportedly has better branching than 'Emerald Lustre' with a lighter colored leaf tip. Of the three planted, one failed to survive the winter. J. Frank Schmidt Nursery in Boring, Oregon, has introduced two new maples that are hybrids of Acer truncatum (Shangtung Maple) and Acer platanoides (Norway Maple). According to Schmidt, both trees will mature at a size slightly smaller than a typical Norway maple, have a finer textured branching habit, and leaves will exhibit shades of orange and red in fall. These new introductions are described below. Acer truncatum X platanoides 'Keithsform' (Norweigan Sunset Maple) - An upright oval tree growing 35 ft tall and 25 ft wide with excellent orange-red fall color. Norwegian Sunset has a particularly nice branch structure and uniform canopy. The trademark name, Norwegian Sunset, reflects the tree's similarity to Norway Maple in growth rate, branch structure, and leaf shape. All test trees survived the first winter. Acer truncatum X platanoides 'Warrenred' (Pacific Sunset Maple) - This upright, spreading tree will grow 30 ft tall, spread 25 ft, and displays outstanding glossy summer foliage that changes to bright red in fall. Pacific Sunset colors earlier and a little brighter than Norwegian Sunset. Branch structure is a little finer textured and more spreading than Norwegian Sunset. All test trees survived the first winter. Crataegus viridis 'Winter King' (Winter King Hawthorn) - Is this ornamental tree hardy for Iowa? After receiving conflicting reports, this tree was included in the trial for closer observation. 'Winter King' has white spring flowers, attractive silver bark, showy and persistent red fruit, and is virtually thornless. All test plans survived their first Iowa winter. Fraxinus pennsylvanica 'Mahle' (Mahle Green Ash) - This selection comes from a tree n K. A. Mahle's yard in Woodbury, Minnesota. Expected to grow 50 to 60 ft tall, 'Mahle' branches exceptionally well as a young tree, forming a broad, oval head at maturity. Foliage is described as a good, glossy green, and the tree is seedless. All test trees survived the winter. Tilia americana 'Fastigiata' (Pyramidal American Linden) - A Bailey Nurseries selection expected to grow to 60 ft. The tree has a narrow, pyramidal form with fragrant yellow flowers. A good candidate for street tree duty. All test trees survived the winter. Selections added to the trial in 1991 include the following: Acer X freemanii 'Autumn Blaze' (Autumn Blaze Maple) - A hybrid of red maple (Acer rubrum) and silver maple (Acer saccharinum) that grows approximately 50 ft tall and 40 ft wide. The tree has a dense, oval head with ascending branches. Summer foliage is a rich green, changing to orange-red in fall. the tree is thought to be more drought tolerant than cultivars of Acer rubrum. Selected by Glenn Jeffers, Fostoria, Ohio, in the late 1960s. Acer platanoides 'Oregon Pride' (Oregon Pride Norway Maple) - An interesting, cut-leaf form of Norway Maple with a gold-bronze fall color. Developing a heavy crown and possessing a rapid growth rate, 'Oregon Pride' will attain heights of 40 to 50 ft. Acer saccharum 'Majesty' (Flax Mill Majest Sugar Maple) - This cultivar was originally found at Flax Mill Nursery in Cambridge, New York. 'Majesty' is characterized by a perfectly symmetrical, ovoid-shaped head, numerous branches (2 to 3 times the branch number of the species), and a rapid growth rate. Thick, dark green leaves turn orange-red in the fall. Trees will grow to heights of 50 to 75 ft and are reportedly free from sunscald and frost-crack injury. Cornus kousa (Kousa Dogwood) - A handsome small specimen tree growing to heights of approximately 20 ft, with an equal or greater spread. Flowers, with their showy, creamy-white bracts, form n early to mid-June. When young, the tree has a vase-shaped growth habit, becoming rounded with a distinct stratified branching pattern as it ages. Leaves are dark green in summer, changing to reddish purple or scarlet in fall. Kousa Dogwood may survive winters in central Iowa, but will it flower dependably? Corylus colurna (Turkish Filbert) - A broadly pyramidal tree with an excellent formal character growing 40 to 50 ft in height with a spread of 20 to 30 ft. Turkish Filbert reportedly will thrive in areas with hot summers and cold winters and is pH adaptable. Leaves are dark green in summer, turning yellow or purple in fall. Insect and disease problems are rare. Fraxinus pennsylvanica 'Prairie Spire' (Prairie Spire Green Ash) - Another hardy, seedless, green ash from North Dakota State University. The tree is compact and columnar when young, becoming narrow pyramidal to elliptical with age, and attaining heights of 50 to 60 ft. Bright golden yellow fall color has been reported. Tilia cordata 'Ronald' (Norlin Linden) - A broadly pyramidal selection of littleleaf linden growing 35 to 45 ft tall. Norlin has a rapid growth rate, strong branches, and is more resistant to sunscald. Dark greenish-brown stems accent the dark green summer foliage. Tilia cordata 'Baileyi' (Shamrock Linden) - Selected and introduced by Bailey Nurseries, this littleleaf linden cultivar is similar to 'Greenspire', but has stouter branchng and a more open canopy. Shamrock will grow 40 to 50 ft tall and take on a broad, conical form." |
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