NC-7 Woody Ornamental Trials

Plant Descriptions of Accessions Offered in 1991

Ampelopsis aconitifolia Bunge var. glabra Diels & Gilg. Three-leaf Monkshoodvine. This vine has delicate leaves that are copper colored at first and then turn deep green.  It is much more finely textured and graceful than the Ampelopsis cordata accessions distributed in past years.  It has suffered little winter injury at Ames, but has not been widely tested in the Midwest.  The plant is especially attractive in autumn when it produces large quantities of yellow-orange berries.

PI 545685 was received in 1984 from Hortus Botanicus Pekinensis, Beijing, China, where it was cultivated.  Probable hardiness USDA Zone 4b.

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Betula nigra L. 'Little King' River Birch. This is an unusual cultivar of a commonly used tree.  This is a low-branched, small tree attaining a height of 7 to 8 feet in a 10-year period.  The tree has a pronounced, rounded-pyramidal habit.  Early spring foliage is a bright green, and the slightly darker summer foliage is glossy.  The exfoliating bark is broken into patterns of pale salmon and shades of cinnamon-red.  'Little King' has excellent resistance to borers, chlorosis and heat stress.  The neat, compact habit of this cultivar should make it ideal for use as specimen plants, borders, low maintenance landscapes and hedges.

Ames 14942 was supplied by Greenwood Propagation, Hebron, Illinois and is promoted by the Chicagoland Grows, Inc. program.  Probable hardiness USDA Zone 4a.

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Cercis canadensis L.  Redbud. This small tree is widely grown in our region, but often suffers winter injury north and northwest of Ames.  This particular native collection from southwestern Iowa should be evaluated for hardiness in areas that have difficulty growing redbuds.

PI 496399 was collected at Lake of Three Fires State Park, Taylor Co., Iowa, elev. 348 meters in 1984 by M.P. Widrlechner.  It was growing on a loam soil, pH 5.8.  Probable hardiness USDA Zone 4b.

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Fraxinus anomala Torrey ex Watson  Single-leaf Ash. This large shrub or small tree is native to the southwestern U.S.  It differs from other ashes in its simple leaves.  It should perform well under xeriscape conditions and on alkaline soils.  It is not widely grown commercially because it has a reputation as being difficult to propagate.  As with some other Fraxinus, it is likely that this species produces seeds with immature embryos that have a long after-ripening period.  Fresh seeds received in 1984 germinated poorly; but when stored at 4 degrees C and retested five years later, they performed much better.

PI 495890 was collected along Rte. 138 in a rocky canyon about 30 miles north of Moab, Grand Co., Utah, elev. 1351 meters, by J. Klett and J. Feucht in 1984.  Soil pH at this site was 8.3 with low organic matter.  Probable hardiness USDA Zone 5a.

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Fraxinus xanthoxyloides (G. Don) Wall. Afghan Ash.  The Afghan Ash is a shrub or small tree adapted to dry areas.  It is rarely grown is the U.S. and has not been well tested in our region.  This species has much smaller leaflets than most other ashes.  The leaves are an attractive, dark gray-green color.  From our experience with these seedlings, we do not expect this tree to have significant fall color.

Ames 10185 was collected at 4 km SW of Brumboret, Northwest Frontier, Pakistan, 35 degrees 38 minutes N, 71 degrees 37 minutes E, elev. 2277 meters by M. Thompson and D. Brenner in 1988.  Probable hardiness USDA Zone 5b.

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Phellodendron amurense. Corktree.  This genus of medium-sized, often broadly spreading, trees is increasing in popularity as a street tree in the upper midwest.  Many cork-trees do not develop good form for urban settings.  This particular accession was collected by Donald Willeke, an individual devoted to urban reforestation.  He located a female cork-tree with particularly attractive form in Minneapolis, Minnesota and collected fruit in 1988.

PI 633677 (Ames 10095) is grown from seeds donated by D. Willeke in January, 1989.  Probable hardiness USDA Zone 3b.

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Quercus gambelii Nutt. x macrocarpa Michx. L. Hybrid Oak.  This is a population of hybrid oaks bred by Miguel Marquez.  The Q. gambelii parent was collected in Ruidoso, New Mexico, elev. 7000 feet; and the Q. macrocarpa came from Kansas City, Missouri.  The supplier reports that this hybrid tends to have a dense branching habit and a central leader.  It is faster growing than Q. gambelii and easier to transplant bare root.  It would be interesting to compare the performance of these hybrids with the Q. gambelii (PI 495905) distributed for testing in 1988.

Plants of Ames 14935 were provided by Oikos Tree Crops, Kalamazoo, Michigan.  Probable hardiness USDA Zone 5a.

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Sorbaria tomentosa (Lindley) Rehder  Lindley False-spiraea.  This false-spiraea is not as well known in our region as is S. sorbifolia.  It tends to be a larger plant, with larger, pendulous inflorescences.  Considering its native range (discussed in detail by Rahn, Nord. J. Bot. 8:557-563, 1989), it is probably more drought tolerant, but less cold hardy than Ural false-spiraea.  In areas with early fall frosts, it may be slow to harden and could suffer foliar damage.  However, in the wild it was noted to have brilliant red leaves in mid-October.

PI 597620 (Ames 10200) was collected 2 km SW of Paloga, Northwest Frontier, Pakistan, 35 degrees 41 minutes N, 72 degrees 4 minutes E, elev. 2400 meters by M. Thompson and D. Brenner in 1988.  Probable hardiness USDA Zone 5a.

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