NC7 Woody Ornamental Trials

Plant Descriptions of Accessions Offered in 2004

Carpinus betulus L. BETULACEAE. European hornbeam. In the Manual of Woody Landscape Plants, Dr. Michael Dirr considers this species to be among “the very finest landscape trees; excellent for screens, hedges, groupings… withstands pruning as well as or better than European beech.” The comparison is fitting, as the two species, hornbeam and beech, are worth comparing. Both have smooth, gray bark, thick, narrowly-ovate to oblong leaves, and sharply pointed vegetative buds. Our Midwestern experience with C. betulus has usually been with the cultivar ‘Fastigiata.’ That and most other selections likely originated from trees cultivated in Western Europe under relatively mild, oceanic climatic conditions. This year’s offering represents another population of wild, forest trees from Ukraine that are likely more tolerant of cold winters and droughty summers than are types commonly cultivated. Also, in contrast to the various compact and fastigiate cultivars that we are accustomed to, this new accession was collected from a stand of particularly large, imposing trees that were a dominant component of the local forest. If possible, please evaluate this accession alongside the two Ukrainian populations that we distributed in 2003.

NA 69993 (Ames 25494) was collected as seed by Mark Widrlechner, Bob Schutzki (our Trial cooperator at Michigan State University), and Vasiliy Yukhnovskyy and Victor Sviatetsky (both of the National Agricultural University of Ukraine) in September 1999, on the edge of a natural forest on the campus of the National Agricultural University, Kyiv, Ukraine; Latitude 50 degrees 23 minutes 14 seconds North; Longitude 30 degrees 30 minutes 40 seconds East; Elevation 140 meters. Trees were growing in well-drained, sandy loam soil with Acer platanoides and Tilia.

Probable hardiness to USDA Zone 4b. Plants of NA 69993 are approximately 50 to 65 cm tall.

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Fraxinus excelsior L. OLEACEAE. European ash. In 1975 and 1979, plant introductions of F. excelsior from the former nation of Yugoslavia were distributed for testing in the NC-7 Trials. From that experience, we learned that Balkan populations of European ash were not particularly well adapted to Midwestern climatic conditions and were typically susceptible to borer attack and serious damage. The ash population available for distribution this year should be much better adapted to environmental stresses (winter cold and summer drought) that may be correlated with borer attack, as it was collected from the eastern edge of its native range in the forest-steppe transition zone near Kharkiv, Ukraine. However, this accession is unlikely to have any resistance to, or tolerance of, the new Emerald Ash Borer that is becoming a pest in southeastern Michigan and nearby areas.

Ames 25520 was collected as seed from a single, large tree with a pyramidal crown by Mark Widrlechner, Bob Schutzki, Vasiliy Yukhnovskyy, and Victor Sviatetsky in September 1999 near Snezhkov, Kharkiv Oblast, Ukraine; Latitude 49 degrees 48 minutes 33 seconds North; Longitude 35 degrees 31 minutes 14 seconds East; Elevation 197 meters. Trees in this population were growing on fairly well-drained, clay loam soil with Quercus robur, Acer campestre, and Acer tataricum. The other ash trees in the population (and generally in this region) did not produce seeds in 1999, evidently because of a late spring freeze.

Probable hardiness to USDA Zone 4b. Most of the plants offered are between 75 and 130 cm tall.

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Prunus tenella Batsch ROSACEAE. Russian almond. Our palette of pink-flowered, low-growing shrubs for the North Central region is rather restricted. A small population of this rhizomatous almond growing at the Minnesota Landscape Arboretum from seeds received from the Main Botanical Garden in Moscow attracted considerable attention during a spring visit some years ago. At the Plant Introduction Station, seedlings grown from the Arboretum’s population have displayed clear pink flowers in considerable profusion followed by clean foliage that colors a bit to red in the fall. While these shrubs do sucker, on heavy soils or in sod suckers should be easy to control. Mature plant height is about 1 to 1.5 meters tall, a flexible size for informal residential landscapes. The fuzzy fruits are curious, but hidden among the foliage.

Ames 24594 was grown from seed donated in 1998 by Nancy Rose from Minnesota Landscape Arboretum, which originally received this population from the Main Botanical Garden (Hortus Botanicus Principalis) in Moscow, Russian Federation.

Probable hardiness to USDA Zone 3. Plants offered are field divisions of established seedlings and are between 30 and 70 cm tall.

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Salix alba L. ‘St. Oedenrode’ SALICACEAE. White willow. White willow is one of relatively few tree species that are widely adapted to the poorly drained soils of our region and those with high water tables. Many different selections have been made from this species with distinctive growth habits, uses, and colors. ‘St. Oedenrode’ is a cultivar with a growth habit that suggests that it was selected for windbreaks and living screens. A subjective evaluation of the Salix collection at the Plant Introduction Station led to its selection for this year’s Trials, based on its uniform, narrow-pyramidal form, lack of cankers or other signs of disease, and clean silvery green foliage that gives a sense of cooling in the middle of summer. While somewhat fastigiate, this cultivar will mature quite large; notes from the donor indicate that its mature height in England is 20 meters. Our field plantings were established in 1993 and are now about 10 meters tall, but only 2.5 meters wide. Mature winter stems are greenish, but new growth is a warm, bronze color.

PI 502252 was obtained from the willow collection of the Long Ashton Research Station in England, and their records indicate that this cultivar was originally collected in the Netherlands.

Probable hardiness to USDA Zone 3. Rooted stem cuttings are approximately 55 cm tall.

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Ulmus parvifolia Jacq. ULMACEAE. Chinese elm. This attractive shade tree, known as Chinese or Lacebark elm, is growing in popularity in the southeastern U.S., where it serves well as a street and park tree. But its utility has been limited in the North Central United States because many selections harden for winter very late in the growing season, making them susceptible to vascular damage. Midwinter cold-hardiness may also be questionable in Zone 4. Its attractive, exfoliating bark and excellent foliage quality provide season-long interest and give us incentives for finding hardier forms.

Ames 24144 was grown from cuttings received from the late Dr. John Pair, Wichita, Kansas, who originally propagated plants from the Kansas state champion tree in Garden City, Kansas. Dr. Jason Griffin, our new cooperator from Wichita, kindly searched Dr. Pair’s files and found that it propagated easily, tended to develop exfoliating bark relatively quickly, and was the most cold-hardy of all clones tested. Dr. Pair also published propagation notes on this clone in the Combined Proceedings of the International Plant Propagators’ Society 42: 431-435 (1992).

Probable hardiness to USDA Zone 5a or 4b. Most of the rooted stem cuttings offered are between 65 and 100 cm tall.

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Links:
Back to list of 2004 plants
All Accessions Evaluated from 1984-Present
NC7 Woody Ornamental Trial Homepage
NC7 Plant Introduction Station Homepage

Please send questions or comments to Mark Widrlechner at nc7mw@ars-grin.gov