Ulmus americana 'Jefferson'

Ulmus americana 'Jefferson'
The original 'Jefferson' elm on the National Mall in Washington, D.C. (March 2014)
SpeciesUlmus americana
Cultivar'Jefferson'
OriginNational Park Service, US

The American elm cultivar Ulmus americana 'Jefferson' was cloned from a tree growing near a path in front of the Freer Gallery of Art, close to the Smithsonian Institution Building ("The Castle") on the National Mall in Washington, D.C.[1] The United States National Park Service, which had planted the tree during the 1930s, cloned it in 1993 after screening tests showed that it possessed an outstanding level of tolerance to Dutch elm disease (DED).[1]

In 2005, the Park Service and the Agricultural Research Service (ARS) of the United States Department of Agriculture jointly released the clone (formerly NPS 3–487) to the nursery trade as 'Jefferson'.[1] The parent tree appears to have remained unscathed by DED in 2014.

Description

'Jefferson' is distinguished by its low, spreading form with arching limbs and broad U-shaped crotches.[2] The parent tree on the National Mall has reached a height of about 68 feet (20.7 m) after 80 years. Ploidy: 2n = 42.

Genetics

Early studies on the parent tree found that the tree has triploid chromosomes, suggesting that it may be a hybrid between the tetraploid American elm and an unknown diploid species.[3] A genetic study that the ARS conducted on the clone at the United States National Arboretum in Washington, D. C., during 2004 confirmed the tree as Ulmus americana, despite having some atypical features.[4]

A subsequent ARS study also confirmed that the tree is a triploid. The study's investigators concluded that a crossing of two American elms, one a tetraploid, the other a less common diploid, had created the tree. The investigators found no triploids among the 81 wild trees that they sampled.[5]

Pests and diseases

The tree proved highly resistant to Dutch elm disease in an ARS trial (as clone N 3487/NA 62001).[6] NA 62001 showed little damage from elm leaf beetle (Xanthogaleruca luteola) feeding during a 2009—2010 survey at an Oklahoma arboretum.[7] 'Jefferson' is susceptible to elm yellows phytoplasma infection, as are other U. americana DED-resistant cultivars and native trees of that species.[8]

The Japanese beetle (Popillia japonica) highly prefers U. americana when feeding.[9] Verticillium wilt had a greater effect on U. americana than it had on all other elms studied in an investigation of that fungal disease.[10]

Cultivation

President George W. Bush and First Lady Laura Bush planting a 'Jefferson' clone outside of the White House in October 2006.

'Jefferson' has not been widely tested beyond Washington D.C. National Elm Trial results were inconclusive and provided no data on ‘Jefferson’ because of an early error in tree identification that occurred in the nursery trade.[11][12] The error may still be causing nurseries to sell 'Princeton' elms that are mislabeled as 'Jefferson', although one can distinguish between the two cultivars as the trees mature.[11][13] The Golden Hill Nursery in Kent introduced 'Jefferson' to the United Kingdom in 2010, but the clone remains rare in cultivation.

On October 2, 2006, President George W. Bush and First Lady Laura Bush planted a clone of the Jefferson elm tree on the west side of the North Grounds center panel of the White House. The clone came from the original tree located on the National Mall.[14]

Accessions

North America

Europe

Notes

  1. ^ a b c Multiple sources:
  2. ^ Sherald, 2009, p. 38. Photographs: (1) Figure 33: "American elm 'Jefferson'. Parent tree on the National Mall in front of the Freer Gallery of Art on Jefferson Drive, flanked on either side by trees vegetatively propagated from it."
    (2) Figure 34: "Young ‘Jefferson’ elms on the National Mall come into full leaf before native American elms."
  3. ^ Multiple sources:
  4. ^ Pooler, Margaret R.; Townsend, A. M. (September 2005). "Research Reports: DNA Fingerprinting of Clones and Hybrids of American elm and Other Elm Species with AFLP Markers". Journal of Environmental Horticulture. 23 (3). Washington, D.C.: Horticultural Research Institute (HRI), the AmericanHort Foundation: 113–117. doi:10.24266/0738-2898-23.3.113. ISSN 0738-2898. LCCN 83643944. OCLC 1057932522. (Jefferson's) identity has been questioned due to its disease tolerance, broad U-shaped branch unions, and bark, branch, and leaf characteristics..
  5. ^ Multiple sources:
  6. ^ Townsend, A. M.; Bentz, S. E.; Douglass, L. W. (March 2005). "Evaluation of 19 American elm Clones for Tolerance to Dutch Elm Disease". Journal of Environmental Horticulture. 23 (1). Washington, D.C.: Horticultural Research Institute (HRI), the AmericanHort Foundation: 21–24. doi:10.24266/0738-2898-23.1.21. ISSN 0738-2898. LCCN 83643944. OCLC 1057932522..
  7. ^ "Elm Leaf Beetle Survey". Clinton, Oklahoma: Sunshine Nursery & Arboretum. Archived from the original on July 19, 2011. Retrieved July 17, 2017.
  8. ^ Multiple sources:
  9. ^ Miller, Fredric; Ware, George; Jackson, Jennifer (April 1, 2001). "Preference of Temperate Chinese Elms (Ulmus spp.) for the Adult Japanese Beetle (Coleoptera: Scarabaeidae)". Journal of Economic Entomology. 94 (2). Oxford University Press (OUP): 445–448. doi:10.1603/0022-0493-94.2.445. ISSN 0022-0493. LCCN 11008063. OCLC 1131914636. PMID 11332837. S2CID 7520439.
  10. ^ Pegg, G. F.; Brady, B. L. (2002). Verticillium Wilts. Wallingford, Oxon, UK: CABI Publishing. p. 291. ISBN 0-85199-529-2. LCCN 2001037313. OCLC 290478616 – via Google Books.
  11. ^ a b 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 from the original (PDF) 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..
  12. ^ 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 November 19, 2025. Retrieved January 26, 2026.
  13. ^ "Jefferson American elm vs. Princeton American elm". Disease-Resistant Elm Identification Guide. University of Minnesota: Urban Forestry Outreach, Research & Extension: The UFore Nursery & Lab. Archived from the original on February 7, 2021. Retrieved February 7, 2021.
  14. ^ Multiple sources:

References

allikas: https://en.wikipedia.org/wiki/Ulmus_americana_%27Jefferson%27