National Elm Trial

The National Elm Trial was an American volunteer effort to evaluate a range of newly developed elm cultivars as replacements for elms destroyed by Dutch elm disease. The Colorado State University College of Agricultural Sciences coordinated the trial.^[1]

The trial began in 2005, but was restricted to elm cultivars commercially available in the United States, unlike the trial conducted by Iowa State University in the 1970s which included the most recent European developments. The trial was conducted for 10 years, with annual assessments of each tree for height, diameter, crown characteristics, and fall color, as well as response to vascular diseases, canker diseases, foliar diseases, insect infestations, bark beetle infestations, and abiotic damages.^[1] Stated goals of the trial were as follows:

Determine the growth and horticultural performance of commercially available elm cultivars resistant to Dutch elm disease in various climate regimes in the United States.
Determine the relative disease, insect, and abiotic stress tolerance of these cultivars.
Promote the propagation and use of elms through local, regional, and national reporting of the trial results to wholesale tree propagators and growers, retail nursery and garden center operators, landscaper designers, arborists, and the general public.^[1]

As of 2007, 19 distinct cultivars were being evaluated in regional trials taking place under the scientific supervision of Auburn University, University of California at Davis, Colorado State University, Purdue University, Iowa State University, Kansas State University, Michigan State University, University of Minnesota, Rutgers University, State University of New York, North Dakota State University, Ohio State University, Utah State University, University of Vermont, Washington State University, and West Virginia University.^[2]

Based on the trial's final ratings, the preferred cultivars of the American elm (Ulmus americana) are ‘New Harmony’ and ‘Princeton’. The preferred cultivars of Asian elms are the Morton Arboretum introductions and ‘New Horizon’.^[1]

List of cultivars included in the trial

American Elm Ulmus americana cultivars: 'Valley Forge', 'New Harmony', 'Princeton', 'Lewis & Clark' (Prairie Expedition), 'Jefferson' (provided no data).^[3]
Chinese Elm Ulmus parvifolia cultivars: BSNUPF (Everclear), 'Emer I' (Athena), 'Emer II' (Allee).
Japanese Elm Ulmus davidiana var. japonica cultivars: 'JFS - Bieberich' (Emerald Sunshine), 'Prospector'.
Hybrid elm cultivars: 'Frontier', 'Homestead', 'Morton' (Accolade), 'Morton Glossy' (Triumph), 'Morton Plainsman' (Vanguard), 'Morton Red Tip' (Danada Charm), 'Morton Stalwart' (Commendation), 'New Horizon', 'Patriot', 'Pioneer'.^[1]^[2]

References

^ ^a ^b ^c ^d ^e (1) "National Elm Trial". Bioagricultural Sciences & Pest Management. Fort Collins, Colorado: Colorado State University College of Agricultural Sciences: Department of Agricultural Biology. 2018. Archived from the original on March 30, 2018..
(2) Griffin, Jason J.; Jacobi, E., William R.; McPherson, Gregory; Sadof, Clifford S.; et al. (2017). "Ten-Year Performance of the United States National Elm Trial" (PDF). Arboriculture & Urban Forestry. 43 (3). International Society of Arboriculture: 107–120. doi:10.17660/ActaHortic.2018.1191.5. ISSN 0567-7572. OCLC 7347020445. Archived (PDF) from the original on February 8, 2021. Retrieved February 7, 2021. Based on the ratings, the preferred cultivars of American elm were 'New Harmony' and 'Princeton', and the preferred cultivars of Asian elm were The Morton Arboretum introductions and 'New Horizon'.
^ ^a ^b (1) "National Elm Trial: Elm Cultivars Currently Being Evaluated". Research: Forest and Shade Tree Health. Fort Collins, Colorado: Colorado State University College of Agricultural Sciences: Forest and Shade Tree Health Lab. June 4, 2007. Archived from the original on February 26, 2008.
(2) "National Elm Trial: Images of Elms Planted At Various Locations Throughout the United States" (photographs). Research: Forest and Shade Tree Health. Fort Collins, Colorado: Colorado State University College of Agricultural Sciences: Forest and Shade Tree Health Lab. June 16, 2008. Archived from the original on September 8, 2008.
^ Zetterstrom, Tom (2017). Pinchot, Cornelia C.; Knight, Kathleen S.; Haugen, Linda M.; Flower, Charles E.; Slavicek, James M. (eds.). "Report From the Street" (PDF). Proceedings of the American Elm Restoration Workshop 2016; 2016 October 25-27; Lewis Center, OH. Newtown Square, PA. United States Department of Agriculture, United States Forest Service, Northern Research Station: 119–121. doi:10.2737/NRS-GTR-P-174. OCLC 1231892730. Gen. Tech. Rep. NRS-P-174. Archived (PDF) from the original on May 1, 2019. Retrieved February 7, 2021. Consumers need to also be aware that a nursery trade mix-up a dozen years ago still plays out in the marketplace, and 'Princeton' elms continue to be sold as 'Jefferson' unknowingly by reputable nurseries from New York to Minnesota. .... National Elm Trial (NET) results were inconclusive and provided no data on 'Jefferson' due to the cultivar mix-up..