Ulmus americana 'Princeton'
'Princeton' aged 6 years, Great Fontley, UK.
The American Elm Ulmus americana cultivar 'Princeton' was originally selected in 1922 by New Jersey nurseryman William Flemer for its aesthetic merit. By coincidence, 'Princeton' was later found to have a moderate resistance to Dutch elm disease.
The tree can grow to > 30 m in height, and is distinguished by its dense, symmetrical, upright form and dark green foliage, ultimately forming a broad umbrella crown. Crotch angles can be acute, with considerable bark inclusion which can lead to branch breakages. The leaves are < 16 cm long by 8 cm broad. 'Princeton' grows quickly, young trees increasing in height by over 1.6 m per annum (d.b.h. by 2.8 cm p.a.) in an assessment at U C Davis as part of the National Elm Trial. The tree commences flowering aged nine years.
Pests and diseases
Testing in laboratory conditions by the United States Department of Agriculture (USDA) in 1992-1993 revealed that this cultivar has a resistance to Dutch elm disease, although the original Princeton Elm, which grew in Princeton Cemetery and was estimated to be over 150 years old, was felled in April 2005 after suffering 60% dieback, attributed by some accounts to Dutch Elm Disease . Moreover, trees introduced to the UK have been found to be susceptible, and many have died. 20 sent to Eisele, Darmstadt, for testing by inoculation with the causal fungus also died. 
Princeton Elms planted in North America are highly prone to leaf damage by Japanese beetles Popillia japonica. Trees grown in the UK have also proven very susceptible to damage by leaf-feeding insects, far more so than native or Asiatic elms. Henry noted that such damage was common to all American Elm Ulmus americana grown in the UK. Trees grown in northern California at U C Davis became infested with leaf curling aphids (Eriosoma), producing copious amounts of honeydew.
Examples of 'Princeton' were planted along Washington Road and another road in Princeton; most of these trees survive to this day  unaffected by disease. The cultivar was more recently chosen to replace elms killed by disease along Pennsylvania Avenue in front of the White House. 'Princeton' is currently being evaluated in the USA as part of the National Elm Trial coordinated by Colorado State University .
The tree has also been reintroduced to the UK. In 2004 three specimens were planted in the gardens of Worcester College, Oxford; Penelope Hobhouse ordered two specimens from the New York Botanical Gardens for planting at her family home, Hadspen, in Somerset. Two years later, 'Princeton' was planted by HRH The Prince of Wales to create the Anniversary Avenue at his residence Highgrove House, however all the trees were removed in 2012 after five died of DED.  In 2009, 100 Princetons were planted in Phoenix Park, Dublin, to replace some of the 2000 native elms lost to Dutch elm disease since the 1980s..
'Princeton' was deemed in need of relatively high pruning requirement in the trials at U C Davis.
- Arnold Arboretum. Acc. nos. 352-91, 561-89.
- Bartlett Tree Experts. Acc. nos. 2001-249, 2001-250, 2001-251, 2001-484, 2001-485, 2003-964.
- Brentwood, Pennsylvania Arboretum. 11 specimens planted as street trees along educational campus, no acc. details available.
- Dawes Arboretum , Newark, Ohio. 2 trees, no acc. details available.
- Holden Arboretum. Acc. nos. 2002-435, 2003-174, 56-908.
- Longwood Gardens. Acc. nos. 2000-0362, 2002-0414, 2003-0032, 2004-0675.
- Morton Arboretum. Acc. no. 125-2008.
- U S National Arboretum , Washington, D.C., USA. Acc. no. 57842
- Brighton & Hove City Council, NCCPG Elm Collection , UK.
- Grange Farm Arboretum, Sutton St. James, Spalding, Lincs. UK. Acc. no. 697.
- Great Fontley, Fareham, UK, Butterfly Conservation Elm Trials plantation, Home Field C1, (planted 2004).
- Royal Horticultural Society Gardens, Wisley, UK. Planted bed WA 0201, c.2002.
- Carlton Plants, LLC , Dayton, Oregon.
- Charles Fiore Nurseries, , Prairie View, Illinois.
- Johnson Farms, , Deerfield, New Jersey.
- Princeton Nurseries , Allentown, New Jersey
- Riveredge Farms , Atlanta, Georgia
- Sharp Top Trees , White, Georgia
- Sunshine Nursery , Clinton, Oklahoma
- The Botany Shop Garden Center , Missouri
- McPherson, G. et al. (2008). National elm trial: Initial report from Northern California. Western Arborist, Fall 2009, pp 32-36.
- Santamour, J., Frank, S. & Bentz, S. (1995). Updated checklist of elm (Ulmus) cultivars for use in North America. Journal of Arboriculture, 21:3 (May 1995), 121-131. International Society of Arboriculture, Champaign, Illinois, USA.
- Smalley, E. B. & Guries, R. P. (1993). Breeding Elms for Resistance to Dutch Elm Disease. Annual Review of Phytopathology Vol. 31 : 325-354. Palo Alto, California.
- Townsend, A. M., Bentz, S. E., and Douglass L. W. (2005). Evaluation of 19 American Elm Clones for Tolerance to Dutch Elm Disease. Journal of Environmental Horticulture, March 2005, Horticultural Research Institute, Washington, D.C.
- Brookes, A. H. (2012). Disease-resistant elm cultivars, Butterfly Conservation trials report, 2nd revision, 2012 Butterfly Conservation, Hants & IoW Branch, England. 
- Brady, C., Condra, J., & Potter, D. (2008) Resistance of Landscape-suitable Elm (Ulmus spp.) Cultivars to Japanese Beetle, Leaf Miners, and Gall Makers. 2008 Research Report, Nursery & Landscape Program, pp 15, 16. University of Kentucky.
- Elwes, H. J. & Henry, A. (1913). The Trees of Great Britain & Ireland. Vol. VII. pp 1848-1929. Private publication. 
- http://www.elmpost.org/2003-03.htm Photograph from 2002 of Princeton elms lining Washington Road in Princeton, New Jersey.