Ulmus americana 'Valley Forge'
Encyclopedia
The American Elm
American Elm
Ulmus americana, generally known as the American Elm or, less commonly, as the White Elm or Water Elm, is a species native to eastern North America, occurring from Nova Scotia west to Alberta and Montana, and south to Florida and central Texas. The American elm is an extremely hardy tree that can...

 Ulmus americana cultivar 'Valley Forge' was raised by the Agricultural Research Service
Agricultural Research Service
The Agricultural Research Service is the principal in-house research agency of the United States Department of Agriculture . ARS is one of four agencies in USDA's Research, Education and Economics mission area...

 in Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

 and released to wholesale nurseries without patent restrictions by the U. S. National Arboretum
United States National Arboretum
The United States National Arboretum is an arboretum in Washington, D.C., operated by the United States Department of Agriculture's Agricultural Research Service as a division of the Henry A. Wallace Beltsville Agricultural Research Center...

 in 1995.

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
University of Georgia
The University of Georgia is a public research university located in Athens, Georgia, United States. Founded in 1785, it is the oldest and largest of the state's institutions of higher learning and is one of multiple schools to claim the title of the oldest public university in the United States...

 criticized the tree's form as 'floppy' http://www.greenbeam.com/rs/nm.pdfs/16338_012.pdf. The bark features greyish, flat-topped ridges, separated by roughly diamond-shaped fissures, and is typical of the species. 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 as part of the National Elm Trial
National Elm Trial
The National Elm Trial is an American volunteer effort to evaluate a range of newly developed elm cultivars as replacements for elms destroyed by Dutch elm disease...

, the tree initially grew comparatively slowly, increasing in height by 0.85 m
Metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

 per annum, although stem development at 2.6 cm d.b.h. was near average.

Pests and diseases

'Valley Forge' is the most Dutch elm disease
Dutch elm disease
Dutch elm disease is a disease caused by a member of the sac fungi category, affecting elm trees which is spread by the elm bark beetle. Although believed to be originally native to Asia, the disease has been accidentally introduced into America and Europe, where it has devastated native...

-resistant of all the American Elm cultivars, although it is not immune. While also very resistant to the elm leaf beetle, Xanthogaleruca luteola
Xanthogaleruca luteola
Xanthogaleruca luteola, commonly known as the Elm Leaf Beetle, is a serious pest of the elm. Indigenous to Europe, it was accidentally introduced to North America. Both the imagines and larvae feed on the emergent leaves of the elm...

http://commons.wikimedia.org/wiki/Xanthogaleruca_luteola like all other American Elms it is susceptible to Elm Yellows
Elm Yellows
Elm Yellows is a plant disease of elm trees that is spread by leafhoppers or by root grafts. Elm Yellows, also known as Elm Phloem Necrosis, is very aggressive, with no known cure. Elm Yellows occurs in the Eastern United States and southern Ontario in Canada. It is caused by phytoplasmas which...

 . In California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 'Valley Forge' has also been found to be susceptible to leaf curling aphids (Eriosoma sp.) which produce honeydew
Honeydew (secretion)
Honeydew is a sugar-rich sticky liquid, secreted by aphids and some scale insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening. Honeydew is particularly common as a secretion in the Hemipteran...

 

The cultivar is only moderately preferred for feeding by the Japanese Beetle Popillia japonica , but the species as a whole
is the most susceptible of all the elms to verticillium wilt
Verticillium wilt
Verticillium Wilt is a wilt disease of over 300 species of eudicot plants caused by one of two species of Verticillium fungus, V. dahliae and V. albo-atrum. Many economically important plants are susceptible including cotton, tomatoes, potatoes, eggplants, peppers and ornamentals, as well as others...

 .

In England, the leaves of 'Valley Forge,' along with those of other American Elm cultivars, remained completely free from Black Spot.

Cultivation

All examples included in 10-year trials at Atherton
Atherton, California
Atherton is an incorporated town in San Mateo County, California, United States. Its population was 6,914 at the 2010 census. In September 2010, Forbes magazine placed Atherton's zip code of 94027 at #2 on its annual list of America's most expensive zip codes, with a median home price of $4,010,200...

, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, 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" . 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
University of Minnesota
The University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...

 proved very difficult to manage, but "settled down" as they matured, adopting a more manageable form and habit . '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 check http://www.elmpost.org/elmpics.htm.

Interim results from the aforementioned trial at U C Davis confirm the tree's high pruning requirement.

'Valley Forge' was introduced to the UK in 2010 and is being assessed by Butterfly Conservation
Butterfly Conservation
Butterfly Conservation is an insect conservation organisation in the United Kingdom. It is one of the largest insect conservation organisations in the world.-History of the Organisation:...

as a potential host plant for the endangered White-letter Hairstreak
White-letter Hairstreak
The White-letter Hairstreak is a butterfly in the family Lycaenidae.-Appearance, behaviour and distribution:A dark little butterfly that spends the majority of its life in the tree tops, feeding on honeydew, making it best observed through binoculars. The uppersides are a dark brown with a small...

; it is not known to have been introduced to Australasia
Australasia
Australasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...

.

Etymology

'Valley Forge' was named for the site near Philadelphia where Washington's forces endured the winter of 1777 during the War of Independence.

Accessions

North America
  • Arnold Arboretum. Acc. no. 180-2003.
  • Bartlett Tree Experts http://www.bartlett.com. Acc. nos. 2001-258, 2001-259, 2001-486, 2001-491, 2003-1010.
  • Brenton Arboretum
    Brenton Arboretum
    The Brenton Arboretum 121 acres is a new arboretum and botanical garden in early stages of development, located at 2629 Palo Circle, Dallas Center, Iowa, USA. The Arboretum aims to display all Iowa native trees and shrubs suitable to the site, as well as many other tree species which can grow in...

    , Dallas Center, Iowa
    Iowa
    Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New...

    . No details available.
  • Dawes Arboretum
    Dawes Arboretum
    The Dawes Arboretum is a non-profit arboretum located outside of Columbus in Newark, Ohio. As one of the premier public gardens in North America, The Dawes Arboretum has over of plant collections, gardens and natural areas...

     http://www.dawesarb.org/collectionsgardens/plant-search.asp, Newark
    Newark, Ohio
    In addition, the remains of a road leading south from the Octagon have been documented and explored. It was first surveyed in the 19th century, when its walls were more apparent. Called the Great Hopewell Road, it may extend to the Hopewell complex at Chillicothe, Ohio...

    , Ohio
    Ohio
    Ohio is a Midwestern state in the United States. The 34th largest state by area in the U.S.,it is the 7th‑most populous with over 11.5 million residents, containing several major American cities and seven metropolitan areas with populations of 500,000 or more.The state's capital is Columbus...

    . 2 trees. No acc. details available.
  • Holden Arboretum
    Holden Arboretum
    The Holden Arboretum, in Kirtland, Ohio, USA, is one of the largest arboretums and botanical gardens in the United States, with over 3,500 acres , 600 acres of which are devoted to collections and gardens. Diverse natural areas and ecologically sensitive habitats make up the rest of the holdings...

    . Acc. nos. 2002-76, 2004-38, 2004-47.
  • Morton Arboretum
    Morton Arboretum
    The Morton Arboretum, in Lisle, Illinois, covers 1,700 acres and is made up of gardens of various plant types and collections of trees from specific taxonomical and geographical areas. It includes native woodlands and a restored Illinois prairie. The Arboretum has over 4,100 different species of...

    . Acc. no. 127-2008, 268-2008.
  • Scott Arboretum
    Scott Arboretum
    Scott Arboretum is an arboretum located across the campus of Swarthmore College, 500 College Avenue, Swarthmore, Pennsylvania. It is open to the public daily without charge....

    . Acc. no. 98-110.
  • Smith College
    Smith College
    Smith College is a private, independent women's liberal arts college located in Northampton, Massachusetts. It is the largest member of the Seven Sisters...

    . Acc. no. 36205.
  • University of Idaho
    University of Idaho
    The University of Idaho is the State of Idaho's flagship and oldest public university, located in the rural city of Moscow in Latah County in the northern portion of the state...

     Arboretum. Acc. no. 2004171.
  • U S National Arboretum
    United States National Arboretum
    The United States National Arboretum is an arboretum in Washington, D.C., operated by the United States Department of Agriculture's Agricultural Research Service as a division of the Henry A. Wallace Beltsville Agricultural Research Center...

     http://www.usna.usda.gov/index.htm, Washington, D.C.
    Washington, D.C.
    Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....

    , USA. Acc. nos. 76510, 68983.

Europe

  • Grange Farm Arboretum
    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....

    , Sutton St. James, Spalding
    Spalding, Lincolnshire
    Spalding is a market town with a population of 30,000 on the River Welland in the South Holland district of Lincolnshire, England. Little London is a hamlet directly south of Spalding on the B1172 road....

    , Lincolnshire
    Lincolnshire
    Lincolnshire is a county in the east of England. It borders Norfolk to the south east, Cambridgeshire to the south, Rutland to the south west, Leicestershire and Nottinghamshire to the west, South Yorkshire to the north west, and the East Riding of Yorkshire to the north. It also borders...

    , UK. Whips planted 2011.
  • Great Fontley Farm, Fareham
    Fareham
    The market town of Fareham lies in the south east of Hampshire, England, between the cities of Southampton and Portsmouth, roughly in the centre of the South Hampshire conurbation.It gives its name to the borough comprising the town and the surrounding area...

    , UK, Butterfly Conservation
    Butterfly Conservation
    Butterfly Conservation is an insect conservation organisation in the United Kingdom. It is one of the largest insect conservation organisations in the world.-History of the Organisation:...

    Elm trials plantation, Home Field, Two whips planted 2010.
  • Longstock Park
    Longstock Park
    Longstock Park is a country estate in the civil parish of Longstock in the Test Valley district of Hampshire, England. Formerly Longstock Manor, of medieval origins, it was purchased by Sir Joshua East in the nineteenth century. On his death, the estate passed to his sons Alfred and Arthur. In...

     http://www.longstocknursery.co.uk/ Arboretum, Longstock
    Longstock
    Longstock is a village and civil parish in Hampshire, England. It lies on the western bank of the River Test, to the north and west of Stockbridge and east of Leckford. The parish has a population of around 450...

    , Stockbridge
    Stockbridge
    -Places:In the United States* Stockbridge, Georgia* Stockbridge, Massachusetts* Stockbridge, Michigan* Stockbridge Township, Michigan* Stockbridge, New York* Stockbridge, Vermont* Stockbridge, Wisconsin* Stockbridge , WisconsinIn the United Kingdom...

    , UK. One juvenile specimen planted 2010.
  • Sir Harold Hillier Gardens
    Sir Harold Hillier Gardens
    The Sir Harold Hillier Gardens is an arboretum comprising 72 hectares accommodating over 42,000 trees and shrubs in about 12,000 taxa, notably a collection of oaks, camellia, magnolia and rhododendron....

    , Ampfield
    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....

    , Hampshire
    Hampshire
    Hampshire is a county on the southern coast of England in the United Kingdom. The county town of Hampshire is Winchester, a historic cathedral city that was once the capital of England. Hampshire is notable for housing the original birthplaces of the Royal Navy, British Army, and Royal Air Force...

    , UK. One juvenile specimen planted 2010. Acc. details not known.

External links

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