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| ACCESSION | PLANT NAME | TAXONOMY | ORIGIN | GENEBANK | IMAGE | AVAILABILITY | RECEIVED | SOURCE TYPE | SOURCE DATE | COLLECTION SITE | COORDINATES | ELEVATION | HABITAT | IMPROVEMENT LEVEL | NARRATIVE | | |
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| 0 | PI 635109 | 'Jefferson' | Ulmus americana L. | Maryland, United States | NC7 | | Not Available | 2004 | DEVELOPED | | | | | | Cultivar | Selected from approximately 600 elms planted on the National Mall in Washington D.C. Triploid selection released jointly by the U.S. National Arboretum and the National Park Service in 2004 because of its disease tolerance and exceptional horticultural characteristics. In experiments conducted in the District of Columbia and at Glenn Dale, Maryland, rooted cuttings have demonstrated high levels of tolerance to both species of the fungus which causes Dutch elm disease. Tolerance of this clone to Dutch elm disease is characterized by a significantly lower extent of foliar symptoms and crown dieback after fungal inoculation, compared to other American elm selections and seedlings. Although not completely immune to the disease, it has an unusually high level of disease tolerance and will contribute to the diversity of elm selections now becoming available in the nursery and landscape industries. A diversity of American elm cultivars will help sustain the species as it begins to regain its stature in the urban forest. Distinguished by dark green leaves which develop earlier in the spring and are retained later in the fall than surrounding American elms. The parent tree is approximately 70 years old (90 cm DBH, 20.6 m tall) and has an expansive umbrella-shaped crown. Branch unions are broad and U-shaped compared to the narrow V unions often found in other American elm trees. The bark is smooth, light to reddish gray in young trees becoming dark gray and fissured in older trees. Summer leaves average 106 mm long by 59 mm wide and are dark green, turning yellow in the autumn. In adaptability trials, it has grown well in the District of Columbia, Maryland, Minnesota, Missouri, New Jersey, Oklahoma, Oregon, and Tennessee, and can be considered adaptable from USDA Zones 4 through 7. Readily propagated by softwood cuttings. Using conventional techniques, 90% of the cuttings collected in mid-May in the District of Columbia usually root within 10 weeks. Excellent choice for planting in urban and suburban sites, large yards, and recreational and industrial parks. It will make a good street tree where there is a wide tree lawn, and where a high arching effect is desired. Its combination of Dutch elm disease tolerance, widespread adaptability, and umbrella-shaped crown will fill important needs of the American public. | 1662748 | PI 635109 |