The

American Elm ''Ulmus americana'', generally known as the American elm or, less commonly, as the white elm or water elm, is a species of elm native to eastern North America, naturally occurring from Nova Scotia west to Alberta and Montana, and south to F ...

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...

''Ulmus americana'' 'Valley Forge' was raised by the Agricultural Research Service in

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

. The tree was released to wholesale nurseries without patent restrictions by the U. S. National Arboretum in 1995 after proving to have a high resistance to

Dutch elm disease Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Although believed to be originally native to Asia, the disease was accidentally introduced into Americas, America ...

. 'Valley Forge' proved only moderately successful in the US National Elm Trial, averaging a survival rate of 66.7% overall, owing largely to environmental factors rather than susceptibility to disease.

Description

The branching is typically upright and arching, creating a broad vase-shaped structure complemented by a dense canopy of leaves. However, Michael A. Dirr, Professor of Horticulture at the

University of Georgia , mottoeng = "To teach, to serve, and to inquire into the nature of things.""To serve" was later added to the motto without changing the seal; the Latin motto directly translates as "To teach and to inquire into the nature of things." , establ ...

criticized the tree's form as 'floppy'. The bark features greyish, flat-topped ridges, separated by roughly diamond-shaped fissures. The dark green leaves are large, < 17 cm (avg. 12 cm) long by < 10 cm (avg. 7.4 cm) broad, typical of the species, turning golden yellow in autumn. In an assessment at

U C Davis The University of California, Davis (UC Davis, UCD, or Davis) is a public land-grant research university near Davis, California. Named a Public Ivy, it is the northernmost of the ten campuses of the University of California system. The instit ...

as part of the National Elm Trial, the tree initially grew comparatively slowly, increasing in height by 0.85 m per annum, although stem development at 2.6 cm

d.b.h. Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bole of a standing tree. DBH is one of the most common dendrometric measurements. Tree trunks are measured at the height of an adult's breast, ...

was near average.McPherson, G. et al. (2008). National elm trial: Initial report from Northern California. ''Western Arborist'', Fall 2009, 32–36. Image: Valley Forge leaf and Euro coin.jpg, Leaf with 1 Euro coin Image: Valley forge autumn colour 2.jpg, Fall color

Pests and diseases

'Valley Forge' has proven the most resistant of all the American Elm cultivars (although it is not immune) to Dutch elm disease. While also very resistant to the elm leaf beetle, ''

Xanthogaleruca luteola ''Xanthogaleruca luteola'', commonly known as the elm-leaf beetle, is a beetle species in the family Chrysomelidae that is native to Europe but invasive in other parts of the world.http://cisr.ucr.edu/elm_leaf_beetle.html - Center for Invasive Sp ...

'

like all other American Elms it is susceptible to

Elm Yellows Elm yellows is a plant disease of elm trees that is spread by leafhoppers or by root grafts."Elm Yellows." Elmcare.Com. 19 Mar. 2008 . Elm yellows, also known as elm phloem necrosis, is very aggressive, with no known cure. Elm yellows occurs in th ...

.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. In

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

'Valley Forge' has also been found to be susceptible to leaf curling

aphids Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

('' Eriosoma'' sp.) which produce honeydew The cultivar is only moderately preferred for feeding by the Japanese Beetle '' Popillia japonica'',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'', 15–16. University of Kentucky. but the species as a whole is the most susceptible of all the elms to

verticillium wilt Verticillium wilt is a wilt disease affecting over 350 species of eudicot plants. It is caused by six species of '' Verticillium'' fungi: ''V. dahliae'', ''V. albo-atrum'', ''V. longisporum'', ''V. nubilum'', ''V. theobromae'' and ''V. tricorp ...

.Pegg, G. F. & Brady, B. L. (2002). ''Verticillium Wilts''. CABI Publishing. In England, the leaves of 'Valley Forge,' along with those of other American Elm cultivars, remained completely free from Black Spot.Brookes, A. H. (2020). ''Great Fontley Elm Trial, 2020 Report''. Butterfly Conservation,

Lulworth Lulworth is the popular name for an area on the coast of Dorset, South West England notable for its castle and cove. However, there is no actual place or feature called simply "Lulworth", the villages are East and West Lulworth and the coastal f ...

, England.

Cultivation

All examples included in 10-year trials at Atherton,

, to evaluate replacements for Californian elms lost to disease were withdrawn after a combination of rapid growth and poor structure condemned the trees as "likely to require more maintenance than most municipalities would find acceptable".Costello, L. R. (2004). A 10-year evaluation of the performance of four elm cultivars in California, U. S. ''Journal of Arboriculture'', March 2004

However, these verdicts may reflect in large measure the fact that they were grown in warm climates but with minimal weed competition. Trees raised in the nursery of the

University of Minnesota The University of Minnesota, formally the University of Minnesota, Twin Cities, (UMN Twin Cities, the U of M, or Minnesota) is a public land-grant research university in the Twin Cities of Minneapolis and Saint Paul, Minnesota, United States. ...

also proved very difficult to manage, but "settled down" as they matured, adopting a more manageable form and habit.Giblin, C. P. & Gillman, J. H. (2006). ''Elms for the Twin Cities: A Guide for Selection and Maintenance.'' University of Minnesota. 'Valley Forge' seems to develop far fewer structural problems in temperate climates further north, where the rate of growth in any given season is much more moderate. Moreover, where grown in the countryside, competing vegetation tends to keep excessively vigorous growth in chec

Interim results from the aforementioned trial at

confirm the tree's high pruning requirement. 'Valley Forge' was introduced to the UK in 2010; it is not known to have been introduced to

Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologi ...

Etymology

'Valley Forge' was named for the site near

Philadelphia Philadelphia, often called Philly, is the List of municipalities in Pennsylvania#Municipalities, largest city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, the List of United States cities by population, sixth-largest city i ...

where Washington's forces endured the winter of 1777 during the

War of Independence This is a list of wars of independence (also called liberation wars). These wars may or may not have been successful in achieving a goal of independence. List See also * Lists of active separatist movements * List of civil wars * List o ...

Accessions

;North America * Arnold Arboretum, US. Acc. no. 180-2003. *Bartlett Tree Expert

US. Acc. nos. 2001-258, 2001-259, 2001-486, 2001-491, 2003-1010. *

Brenton Arboretum The Brenton Arboretum is a 141-acre arboretum and public garden in Dallas Center, Iowa, United States, established in 1997. The arboretum displays 175 native Iowa trees and shrubs suitable to the site, as well as many other tree species which ca ...

Dallas Center Dallas Center is a city in Dallas County, Iowa, United States. The population was 1,901 during the 2020 census. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area. History Dallas Center got its start in the year 1869, f ...

Iowa Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to th ...

, US. No details available. *

Dawes Arboretum The Dawes Arboretum is a nonprofit arboretum located in Newark, Ohio. It includes nearly of plant collections, gardens and natural areas. The site includes approximately 12 miles (19 km) of hiking trails and roadways for a four-mile (6&nbs ...

br>
Newark, Ohio, Newark,

Ohio Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...

, US. 2 trees. No acc. details available. *

Holden Arboretum The Holden Arboretum, in Kirtland, Ohio, is one of the largest arboreta and botanical gardens in the United States, with more than , including devoted to collections and gardens. Diverse natural areas and ecologically sensitive habitats make up t ...

, US. Acc. nos. 2002-76, 2004–38, 2004-47. *

Morton Arboretum The Morton Arboretum, in Lisle, Illinois, United States, is a public garden, and outdoor museum with a library, herbarium, and program in tree research including the Center for Tree Science. Its grounds, covering 1,700 acres (6.9 square kilometres ...

, US. Acc. no. 127-2008, 268-2008, 214-2012. *

Scott Arboretum Scott Arboretum () is an arboretum coterminous with the campus of and operated by Swarthmore College. It is open to the public daily without charge. The arboretum was established and endowed by the Scott family in 1929 in honor of Arthur Hoyt Sc ...

, US. Acc. no. 98-110. * Smith College, US. Acc. no. 36205. *

University of Idaho The University of Idaho (U of I, or UIdaho) is a public land-grant research university in Moscow, Idaho. It is the state's land-grant and primary research university,, and the lead university in the Idaho Space Grant Consortium. The Universit ...

Arboretum, US. Acc. no. 2004171. * U S National Arboretumbr>

Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...

, US. Acc. nos. 76510, 68983.

Europe

Grange Farm Arboretum The Grange Farm Arboretum is a small private arboretum comprising 3 hectares accommodating over 800 trees, mostly native and ornamental species or cultivars, notably oaks, ashes, walnuts and elms, growing on a calcareous loam.Ostler, J. (2009) ...

Sutton St James Sutton St James is a village and civil parish in the South Holland district of Lincolnshire, England, about south-west of Long Sutton. Lying in the Lincolnshire Fens, Sutton St James did not exist at the time of the 1086 ''Domesday Book''. Su ...

, Spalding,

Lincolnshire Lincolnshire (abbreviated Lincs.) is a Counties of England, county in the East Midlands of England, with a long coastline on the North Sea to the east. It borders Norfolk to the south-east, Cambridgeshire to the south, Rutland to the south-we ...

, UK. Whips planted 2011. Acc. no. 1056 *Great

Fontley Funtley – from the Anglo-Saxon, "Funtaleg", "spring field (clearing)", is a hamlet or exurb north of Fareham, Hampshire, England. It forms a projection towards the South Downs National Park and is generally included within Fareham's populat ...

, Fareham, UK, '' Butterfly Conservation'' Elm trials plantation, Home Field, two whips planted 2010. * Sir Harold Hillier Gardens,

Ampfield Ampfield is a village and civil parish in the Borough of Test Valley in Hampshire, England, between Romsey, Eastleigh, and Winchester. It had a population at the 2001 census of 1,474, increasing to 1,583 at the 2011 Census. Geography Ampfield ...

Hampshire Hampshire (, ; abbreviated to Hants) is a ceremonial and non-metropolitan county in western South East England on the coast of the English Channel. Home to two major English cities on its south coast, Southampton and Portsmouth, Hampshire ...

, UK. One planted 2010. Acc. no. 2010.0383 * Wijdemeren city council, The Netherlands, Elm collection, two planted 2016, Rading 1, Loosdrecht.

Nurseries

Europe

*Van Den Berk (UK) Ltd.

London, UK

References

External links

*http://www.extension.iastate.edu/Publications/SUL4.pdf Summary, inc. photographs, of elm cultivars resistant to Dutch elm disease available in the United States.
Saving the American Elm, by Bruce Carley
*http://www.sunshinenursery.com/elms.htm Review of current elm selections in the United States. {{Elm species, varieties, hybrids, hybrid cultivars and species cultivars , state=collapsed American elm cultivar Ulmus articles with images Ulmus