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| Ulmus americana | |
|---|---|
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| Ulmus americana (American elm) inNorthampton, Massachusetts | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Rosales |
| Family: | Ulmaceae |
| Genus: | Ulmus |
| Subgenus: | U.subg. Oreoptelea |
| Section: | U.sect. Blepharocarpus |
| Species: | U. americana |
| Binomial name | |
| Ulmus americana | |
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| Synonyms | |
List
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Ulmus americana, generally known as theAmerican elm or, less commonly, as thewhite elm orwater elm,[a] is a species ofelm native to easternNorth America. The trees can live for several hundred years. It is a veryhardy species that can withstand low winter temperatures, but it is affected byDutch elm disease.
The wood was seldom utilized until the advent of mechanical sawing. It is thestate tree of Massachusetts and North Dakota.
The American elm is adeciduous tree which, under ideal conditions, can grow to heights of 21 to 35 meters (69 to 115 feet).[3] The trunk may have adiameter at breast height (dbh) of more than 1.2 m (4 ft), supporting a high, spreading umbrella-like canopy. Theleaves are alternate, 7–20 centimeters (3–8 inches) long, with double-serrate margins and an oblique base. The leaves turn yellow in the fall. Theperfect flowers are small, purple-brown and, being wind-pollinated,apetalous. The flowers are alsoprotogynous, the female parts maturing before the male, thus reducing, but not eliminating, self-fertilization,[4] and emerge in early spring before the leaves. Thefruit is a flatsamara 2 cm (3⁄4 in) long by 1.5 cm broad, with a circular papery wing surrounding the single4.5 millimeters (1⁄8 inch)seed. As in the closely relatedUlmus laevis (European white elm), the flowers and seeds are borne on 1–3 cm long stems. American elm is wholly insensitive to daylight length (photoperiod), and will continue to grow well into autumn until injured by frost.[5]Ploidy is2n = 56, or more rarely,2n = 28.[6]
For over 80 years,U. americana had been identified as atetraploid, i.e. having double the usual number of chromosomes, making it unique within the genus. However, a study published in 2011 by theAgricultural Research Service of theUnited States Department of Agriculture revealed that about 20% of wild American elms arediploid and may even constitute another species. Moreover, several triploid trees known only in cultivation, such as'Jefferson', are possessed of a high degree of resistance to DED, which ravaged American elms in the 20th century. This suggests that the diploid parent trees, which have markedly smaller cells than the tetraploid, may too be highly resistant to the disease.[7][8]
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Ulmus americana was first described and named byCarl Linnaeus in hisSpecies Plantarum, published in 1753. Nosubspecies orvarieties are currently recognized.
The American elm is native to easternNorth America, occurring fromNova Scotia west toAlberta andMontana, and south toFlorida and centralTexas. It is an extremelyhardy tree that can withstand winter temperatures as low as −40 °C (−40 °F).[9]
The species occurs naturally in an assortment of habitats, most notably rich bottomlands, floodplains, stream banks, and swampy ground, although it also often thrives on hillsides, uplands and other well-drained soils.[10] On more elevated terrain, as in theAppalachian Mountains, it is most often found along rivers.[11] The species'wind-dispersed seeds enable it to spread rapidly as suitable areas of habitat become available.[10] American elm fruits in late spring (which can be as early as February and as late as June depending on the climate), the seeds usually germinating immediately, with nocold stratification needed (occasionally some might remain dormant until the following year). The species attains its greatest growth potential in the Northeastern US, while elms in the Deep South andTexas grow much smaller and have shorter lifespans, although conversely their survival rate in the latter regions is higher owing to the climate being less favorable to the spread of DED.[citation needed]
In the United States, the American elm is a principal member of four major forest cover types:black ash-American elm-red maple;silver maple-American elm;sugarberry-American elm-green ash; andsycamore-sweetgum-American elm, with the first two of these types also occurring in Canada.[12] Asugar maple-ironwood-American elm cover type occurs on some hilltops nearTémiscaming,Quebec.[13]
The leaves of the American elm serve as food for thelarvae of a number of species ofLepidoptera. These include such butterflies as the Eastern Comma (Polygonia comma), Question Mark (Polygonia interrogationis), Mourning Cloak (Nymphalis antiopa), Painted Lady (Vanessa cardui) and Red-spotted Purple (Limenitis arthemis astyanax), as well as such moths as the Columbian Silkmoth (Hyalophora columbia) and the Banded Tussock Moth (Pale Tiger Moth) (Halysidota tessellaris).[14]
The American elm is susceptible to Dutch Elm Disease and toelm yellows. In North America, there are three species of elm bark beetles: one native,Hylurgopinus rufipes ("native elm bark beetle"); and two invasive,Scolytus multistriatus ("smaller European elm bark beetle") andScolytus schevyrewi ("banded elm bark beetle"). Although intensive feeding by elm bark beetles can kill weakened trees,[15] their main impact is as vectors of DED.
American elm is also moderately preferred for feeding and reproduction by the adult elm leaf beetleXanthogaleruca luteola[16] and highly preferred for feeding by the Japanese beetlePopillia japonica[17] in the United States.
U. americana is also the most susceptible of all the elms toverticillium wilt,[18] whose external symptoms closely mimic those of DED. However, the condition is far less serious, and afflicted trees should recover the following year.
Dutch elm disease (DED) is afungaldisease that has ravaged the American elm, causing catastrophic die-offs in cities across the range. It has been estimated that only approximately 1 in 100,000 American elm trees is DED-tolerant, most known survivors simply having escaped exposure to the disease.[19] However, in some areas still not infested by DED, the American elm continues to thrive, notably inFlorida,Alberta andBritish Columbia. There is a notable grove of old American elm trees inManhattan'sCentral Park. The trees there were apparently spared because of the grove's isolation in such an intensely urban setting.[citation needed]
The American elm is particularly susceptible to disease because the period of infection often coincides with the period, approximately 30 days, of rapid terminal growth when new springwood vessels are fully functional. Spores introduced outside of this period remain largely static within thexylem and are thus relatively ineffective.[20]
The American elm's biology in some ways has helped to spare it from obliteration by DED, in contrast to what happened to theAmerican chestnut with thechestnut blight. The elm's seeds are largely wind-dispersed, and the tree grows quickly and begins bearing seeds at a young age. It grows well along roads or railroad tracks, and in abandoned lots and other disturbed areas, where it is highly tolerant of most stress factors. Elms have been able to survive and to reproduce in areas where the disease had eliminated old trees, although most of these young elms eventually succumb to the disease at a relatively young age. There is some reason to hope that these elms will preserve the genetic diversity of the original population, and that they eventually will hybridize with DED-resistant varieties that have been developed or that occur naturally. After 20 years of research, American scientists first developed DED-resistant strains of elms in the late 1990s.[19]
Elms in forest and other natural areas have been less affected by DED than trees in urban environments due to lower environmental stress from pollution and soil compaction and due to occurring in smaller, more isolated populations.
Fungicidal injections can be administered to valuable American elms, to prevent infection. Such injections generally are effective as a preventive measure for up to three years when performed before any symptoms have appeared, but may be ineffective once the disease is evident.
In the 19th and early 20th century, American elm was a commonstreet and park tree owing to its tolerance of urban conditions, rapid growth, and graceful form. This however led to extreme overplanting of the species, especially to form living archways over streets, which ultimately produced an unhealthymonoculture of elms that had no resistance to disease and pests. Elms do not naturally form pure stands and trees used in landscaping were grown from a handful of cultivars, causing extremely low genetic diversity.[21] These trees' rapid growth and longevity, leading to great size within decades, made them popular before the advent of DED.[10] Ohio botanist William B. Werthner, discussing the contrast between open-grown and forest-grown American elms, noted that:
"In the open, with an abundance of air and light, the main trunk divides into several leading branches which leave the trunk at a sharp angle and continue to grow upward, gradually diverging, dividing and subdividing into long, flexible branchlets whose ends, at last, float lightly in the air, giving the tree a round, somewhat flattened top of beautifully regular proportions and characteristically fine twiggery."[10]
It is this distinctive growth form that is so valued in the open-grown American elms of street plantings, lawns, and parks; along most narrower streets, elms planted on opposite sides arch and blend together into a leafy canopy over the pavement. However, elms can assume many different sizes and forms depending on the location and climate zone. In 1926 the Klehm Nurseries ofArlington Heights, Illinois, wrote: "American Elms grown in the regular way from seedlings show extreme variability, growing up into trees of all shapes, some of them being very slow in growth while others are moderately rapid in development. The shapes run all the way from the true open excurrent growth to globular, or flat-topped, or pendant. As regards foliage, the leaves are from small to medium large, some shedding early and others late. This condition makes it difficult for the landscape architect to choose just the right trees to obtain the effect desired."[22] The classic vase-shaped elm was mainly the result of selective breeding of a few cultivars and is much less likely to occur in the wild.[23]
American elms have been planted in North America beyond its natural range as far north as centralAlberta. It also survives low desert heat atPhoenix, Arizona.
Introductions across the Atlantic rarely prospered, even before the outbreak of DED. Introduced to theUK byJames Gordon[1] in 1752, the American elm was noted to be far more susceptible to insect foliage damage than native elms.[24] The tree was propagated and marketed in the UK by the Hillier & Sons nursery,Winchester, Hampshire from 1945, with 450 sold in the period 1962 to 1977 when production ceased with the advent of the more virulent form of Dutch elm disease.[25][26] Introduced toAustralasia, the tree was listed by Australian nurseries in the early 20th century. It is known to have been planted along theAvenue of Honour atBallarat, Victoria and the Avenue of Honour inBacchus Marsh, Victoria. In addition, a heritage-listed planting of American elms can be found along Grant Crescent inGriffith, Australian Capital Territory.[27] American elms are only rarely found in New Zealand.[28]
Numerouscultivars have been raised, originally for their aesthetic merit but more recently for their resistance to Dutch elm disease[29] The total number of named cultivars is circa 45, at least 18 of which have probably been lost to cultivation as a consequence of DED or other factors:
and others.[30]
The disease-resistant selections made available to commerce to date include'Valley Forge','New Harmony','Princeton','Jefferson','Lewis & Clark','Miller Park','St. Croix','Endurance', and a set of six different clones collectively known as'American Liberty'.[31] TheUnited States National Arboretum released 'Valley Forge' and 'New Harmony' in late 1995, after screening tests performed in 1992–1993 showed both had unusually high levels of resistance to DED. 'Valley Forge' performed especially well in these tests.[32]
'Princeton' has been in occasional cultivation since the 1920s. 'Princeton' gained renewed attention after its performance in the 1992–1993 screening tests showed that it also had a high degree of disease resistance. A later test performed in 2002–2003 confirmed the disease resistance of 'Princeton', 'Valley Forge' and 'New Harmony', as well as that of 'Jefferson'. Thus far, plantings of these four varieties generally appear to be successful.
In 2005, approximately 90 'Princeton' elms were planted alongPennsylvania Avenue in front of theWhite House inWashington, D.C. The trees, whose maintenance theNational Park Service (NPS) manages, remain healthy and are thriving.[33] However, it has been noted thatU. americana cultivars are not recommended for more than singular plantings as they have unresolved DED and elm yellows concerns.[34]
It has also been noted that monoculture plantings ofU. americana cultivars, such as those along Pennsylvania Avenue, have disproportionate vulnerabilities to disease.[34] Further, long-term studies of 'Princeton' in Europe and the United States have suggested that the cultivar's resistance to DED may be limited (seePests and diseases of 'Princeton').
TheNational Elm Trial evaluated 19 elm cultivars commercially available in the United States in scientific plantings throughout the nation to assess and compare the strengths and weaknesses of each. The trial, which started in 2005, lasted for ten years. Based on the trial's final ratings, the preferred cultivars ofU. americana are 'New Harmony' and 'Princeton'.[35]
'Jefferson' was released to wholesale nurseries in 2004 and is becoming increasingly available for planting. However, 'Jefferson' has not been widely tested beyond Washington, D.C. The National Elm Trial provided no data on ‘Jefferson’ because an error in tree identification had occurred earlier in the nursery trade.[36] 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.[34][37]
In 2007, the 'Elm Recovery Project'[38] from theUniversity of Guelph in Ontario, Canada, reported that cuttings from healthy surviving old elms surveyed across Ontario had been grown to produce a bank of resistant trees, isolated for selective breeding of highly resistant cultivars.[39]
In 1993, Mariam B. Sticklen and James L. Sherald reported the results of NPS-funded experiments conducted atMichigan State University inEast Lansing that were designed to applygenetic engineering techniques to the development of DED-resistant strains of American elm trees.[40] In 2007, AE Newhouse and F Schrodt of theState University of New York College of Environmental Science and Forestry inSyracuse reported that youngtransgenic American elm trees had shown reduced DED symptoms and normalmycorrhizal colonization.[41]
Thousands of attempts to cross the American elm with the Siberian elmU. pumila failed.[42] Attempts at theArnold Arboretum using ten other American, European and Asiatic species also ended in failure, attributed to the differences inploidy and operationaldichogamy,[4] although the ploidy factor has been discounted by other authorities.[43]
Success was eventually achieved with the autumn-flowering Chinese elmUlmus parvifolia by the late Prof.Eugene Smalley towards the end of his career at theUniversity of Wisconsin–Madison after he overcame the problem of keeping Chinese elm pollen alive until spring.[44] Only one of the hybrid clones was commercially released, as'Rebella' in 2011 by the German nursery Eisele GmbH; the clone is not available in the United States.
Other artificial hybridizations with American elm are rare, and now regarded with suspicion. Two such alleged successes by the nursery trade were'Hamburg', and'Kansas Hybrid', both with Siberian elmUlmus pumila. However, given the repeated failure with the two species by research institutions, it is now believed that the "American elm" in question was more likely to have been the red elm,Ulmus rubra.[45]
![[icon]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aWiki_letter_w_cropped.svg) | This sectionneeds expansion. You can help byadding to it.(October 2011) |
The American elm's wood is coarse, hard, and tough, with interlacing, contorted fibers that make it difficult to split or chop, and cause it to warp after sawing.[10] Accordingly, the wood originally had few uses, save for making hubs forwagon wheels.[10] Later, with the advent of mechanical sawing, American elm wood was used forbarrel staves,trunk-slats, andhoop-poles, and subsequently became fundamental to the manufacture of woodenautomobile bodies, with the intricate fibers holdingscrews unusually well.[10]
Young twigs and branchlets of the American elm have tough, fibrous bark that has been used as a tying and binding material, even forrope swings for children, and also for makingwhips.[10]
Mary Eleanor Wilkins Freeman, in her 1903 book of short stories,Six Trees, wrote of the American elm:
There was not in the whole countryside another tree which could compare with him. He was matchless. Never a stranger passed the elm but stopped, and stared, and said or thought something about it. Even dull rustics looked, and had a momentary lapse from vacuity.[46]
On 21 March 1941 the American elm was made thestate tree of Massachusetts. The designation was in commemoration of the fact that George Washington reputedly took command of the Continental Army under an elm.[47]
A number of mostly small to medium-sized American elms now survive in woodlands, suburban areas, and occasionally cities, where the survivors have often been relatively isolated from other elms and thus spared a severe exposure to the fungus. For example, in Central Park andTompkins Square Park inNew York City, stands of several large elms originally planted byFrederick Law Olmsted survive because of their isolation from neighboring areas in New York where there had been heavy mortality.[48] The Olmsted-designed park system inBuffalo, New York,[49] did not fare as well.
A row of mature American elms lines Central Park along the entire length of Fifth Avenue from 59th to 110th Streets.[50] InAkron, Ohio, there is a very old elm tree that has not been infected. In historical areas ofPhiladelphia, Pennsylvania, there are also a few mature American elms still standing — notably inIndependence Square and the Quadrangle at theUniversity of Pennsylvania, and also at the nearby campuses ofHaverford College,Swarthmore College, andPennsylvania State University, believed to be the largest remaining stand in the country.[51]
There are several large American Elm trees in western Massachusetts. A large specimen, which stands on Summer Street in theBerkshire County town ofLanesborough, Massachusetts, has been kept alive by antifungal treatments.Rutgers University has preserved 55 mature elms on and in the vicinity ofVoorhees Mall on the College Avenue Campus inNew Brunswick, New Jersey in addition to seven disease-resistant trees that have been planted in this area of the campus in recent years.[52]
The largest surviving urban forest of American elms in North America is believed to be in the city ofWinnipeg, Manitoba, Canada, where close to 200,000 elms remain. The city of Winnipeg spends $3 million annually to aggressively combat the disease utilizingDursban Turf[53] and theDutch Trig vaccine,[54] losing 1,500–4,000 trees per year.
Governmental agencies, educational institutions or other organizations in most of the states that are within the United States maintain lists of champion or big trees that describe the locations and characteristics of those states' largest American elm trees (seeList of state champion American elm trees). The current U.S. national champion American elm tree is located inIberville Parish, Louisiana. When measured in 2010, the tree had a trunk circumference of 820 cm (324 in), a height of 34 m (111 ft) and an average crown spread of 24 m (79 ft).[55]
The currentTree Register of the British Isles (TROBI) champion grows inAvondale Forest nearRathdrum,County Wicklow, Ireland. The tree had a height of 22.5 m (74 ft) and a dbh of 98 cm (39 in) (circumference of 308 cm or 121 in) when measured in 2000.[56] The tree replaced on the register a larger champion located in Woodvale Cemetery inSussex, England, which in 1988 had a height of 27 metres (89 ft) and a diameter of 115 cm (45 in) or circumference of 361 cm (142 in).[57]
A prime example of the species was the Sauble Elm,[58] which grew beside the banks of theSauble River inOntario, Canada, to a height of 43 m (140 ft), with a dbh of 196 cm (77 in) before succumbing to DED; when it was felled in 1968, a tree-ring count established that it had germinated in 1701. Other large or otherwise significant American elm trees have included:
The Treaty Elm,Philadelphia,Pennsylvania. In what is nowPenn Treaty Park, the founder ofPennsylvania,William Penn, is said to have entered into a treaty of peace in 1683 with thenativeLenape Turtle Clan under a picturesque elm tree immortalized in a painting byBenjamin West. West made the tree, already a local landmark, famous by incorporating it into his painting after hearing legends (of unknown veracity) about the tree being the location of the treaty. No documentary evidence exists of any treaty Penn signed beneath a particular tree. On March 6, 1810 a great storm blew the tree down. Measurements taken at the time showed it to have a circumference of 24 feet (7.3 m), and its age was estimated to be 280 years. Wood from the tree was made into furniture, canes, walking sticks and various trinkets that Philadelphians kept as relics.[59]
TheWashington Elm,Cambridge, Massachusetts.George Washington is said to have taken command of the AmericanContinental Army under the Washington Elm in Cambridge on July 3, 1775. The tree survived until the 1920s and "was thought to be a survivor of the primeval forest". In 1872, a large branch fell from it and was used to construct a pulpit for a nearby church.[60] The tree, an American white elm, became a celebrated attraction, with its own plaque, a fence constructed around it and a road moved in order to help preserve it.[61] The tree was cut down (or fell—sources differ) in October 1920 after an expert determined it was dead.
The city of Cambridge had plans for it to be "carefully cut up and a piece sent to each state of the country and to the District of Columbia and Alaska," according toThe Harvard Crimson.[62] As late as the early 1930s, garden shops advertised that they had cuttings of the tree for sale, although the accuracy of the claims has been doubted. A Harvard "professor of plant anatomy" examined the tree rings days after the tree was felled and pronounced it between 204 and 210 years old, making it at most 62 years old when Washington took command of the troops at Cambridge. The tree would have been a little more than two feet in diameter (at 30 inches above ground) in 1773.[63]
In 1896, an alumnus of theUniversity of Washington, obtained a rooted cutting of the Cambridge tree and sent it to Professor Edmund Meany at the university. The cutting was planted, cuttings were then taken from it, including one planted on February 18, 1932, the 200th anniversary of the birth of George Washington, for whom Washington state is named. That tree remains on the campus of the Washington State Capitol. Just to the west of the tree is a small elm from a cutting made in 1979.[61]
George Washington's Elm,Washington, D.C. George Washington supposedly had a favorite spot under an elm tree near the United States Capitol Building from which he would watch construction of the building. The elm stood near the Senate wing of the Capitol building until 1948.[60]
TheLogan Elm that stood nearCircleville, Ohio, was one of the largest American elms in the world. The 65-foot-tall (20 m) tree had a trunk circumference of 24 feet (7.3 m) and a crown spread of 180 feet (55 m).[64] Weakened by DED, the tree died in 1964 from storm damage.[64] TheLogan Elm State Memorial commemorates the site and preserves various associated markers and monuments.[64] According to tradition,Chief Logan of theMingo tribe delivered a passionate speech at a peace-treaty meeting under this elm in 1774.[64][65]
Another notable American elm, namedHerbie, was the tallest American elm in New England until it was cut down on January 19, 2010, after it succumbed to DED. Herbie was 110 feet (34 m) tall at its peak and had a circumference of 20.3 feet (6.2 m), or a diameter of approximately 6.5 feet (2.0 m). The tree stood inYarmouth, Maine, where it was cared for by the town's tree warden, Frank Knight.[66]
When cut down, Herbie was 217 years old. Herbie's wood is of interest todendroclimatologists, who will use cross-sections of the trunk to help answer questions about climate during the tree's lifetime.[66]
The Glencorradale Elm onPrince Edward Island, Canada, is a surviving wild elm believed to be several hundred years old.[67]
An American elm located in a parking lot directly across the street from theAlfred P. Murrah Federal Building in Oklahoma City survived theOklahoma City bombing on April 19, 1995, that killed 168 people and destroyed the Murrah building. Damaged in the blast, with fragments lodged in its trunk and branches, it was nearly cut down in efforts to recover evidence. However, nearly a year later the tree began to bloom. Then known as the Survivor Tree, it became an important part of theOklahoma City National Memorial, and is featured prominently on the official logo of the memorial.[68]
TheParliament Hill Elm was planted inOttawa, Canada, in the late 1910s or early 1920s whenCentre Block was rebuilt following the Great fire of 1916. The tree grew for approximately a century next to a statue ofJohn A. Macdonald and was one of the few in the region to survive the spread of DED in the 1970s and 1980s.[69] Despite protests from Ottawa area environmentalists and resistance from OppositionMembers of Parliament the tree was removed in April 2019 to make way for new Centre Block renovations.[70]
New York City'sCentral Park is home to approximately 1,200 American elms. The oldest of these elms were planted during the 1860s byFrederick Law Olmsted, making them among the oldest stands of American elms in the world. The trees are particularly noteworthy along the Mall and Literary Walk, where four lines of American elms stretch over the walkway forming a cathedral-like covering. A part of New York City'surban ecology, the elms improve air and water quality, reduce erosion and flooding, and decrease air temperatures during warm days.[71]
While the stand is still vulnerable to DED, in the 1980s theCentral Park Conservancy undertook aggressive countermeasures such as heavy pruning and removal of extensively diseased trees. These efforts have largely been successful in saving the majority of the trees, although several are still lost each year. Younger American elms that have been planted in Central Park since the outbreak are of the DED-resistant 'Princeton' and 'Valley Forge' cultivars.[72]
Several rows of American elm trees that the National Park Service first planted during the 1930s line much of the 1.9 miles (3.0 km) length of theNational Mall inWashington, D.C. DED first appeared on the trees during the 1950s and reached a peak in the 1970s. The NPS used a number of methods to control theepidemic, includingsanitation,pruning, injecting trees withfungicide and replanting with DED-resistant cultivars. The NPS combated the disease's local insectvector, the smaller European elm bark beetle (Scolytus multistriatus), by trapping and by spraying withinsecticides. As a result, the population of American elms planted on the Mall and its surrounding areas has remained intact for more than 80 years.[73]
The nobility and arching grace of the American Elm in its heyday, on farms, in villages, in towns and on campuses, were celebrated in the books of photographs ofWallace Nutting (Massachusetts Beautiful, N.Y. 1923, and other volumes in the series) and ofSamuel Chamberlain (The New England Image, New York, 1962).Frederick Childe Hassam is notable among painters who have depicted American Elm.
![Scribner's magazine [1887]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aScribner%2527s_magazine_(1887)_(14778695871).jpg)
![Frederick Childe Hassam, 'Washington Arch, Spring' [1893]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aHassam_Washington_Arch_Spring.jpg)
![Frederick Childe Hassam, 'Church at Old Lyme' [1905]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aChurch_at_Old_Lyme_Childe_Hassam.jpeg)
![Frederick Childe Hassam, 'The East Hampton Elms in May' [1920]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aChilde_Hassam%2527s_1920_oil%2c_The_East_Hampton_Elms_in_May.jpg)
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![American elm in Charlottetown, Prince Edward Island, Canada (August 2019). This tree was downed by Hurricane Fiona in 2022.[75]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aAmerican_Elm_Tree%2c_Charlottetown%2c_PEI_-_August_2019.jpg)
![American elm at Dartmouth College in Hanover, New Hampshire (June 2015) This tree was cut down in 2022 due to Dutch Elm disease.[76]](/mt/?noimg=&dark=on&url=https%3a%2f%2fwikipedia.org%2fwiki%2fFile%3aAmerican_Elm%2c_Dartmouth_College%2c_Hanover%2c_NH_(June_2015).jpg)
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Accolade® (Ulmus davidiana var. japonica 'Morton') .... Commendation™ (Ulmus 'Morton Stalwart') .... Danada Charm™ (Ulmus 'Morton Red Tip') .... Emerald Sunshine® (Ulmus davidiana var. japonica 'JFS-Bieberich') .... Frontier (Ulmus 'Frontier') .... Homestead (Ulmus 'Homestead'): .... Jefferson (Ulmus americana 'Jefferson') .... New Harmony (Ulmus americana 'New Harmony') .... New Horizon (Ulmus 'New Horizon') .... Patriot (Ulmus 'Patriot') .... Pioneer (Ulmus 'Pioneer') .... Prairie Expedition® (Ulmus americana 'Lewis & Clark'): .... Princeton (Ulmus americana 'Princeton') .... Prospector (Ulmus davidiana var. japonica 'Prospector') .... Regal (Ulmus 'Regal') .... Triumph™ (Ulmus 'Morton Glossy') .... Valley Forge (Ulmus americana 'Valley Forge') .... Vanguard™ (Ulmus 'Morton Plainsman').
Because of unresolved DED and elm yellows concerns, American elm cultivars are not recommended for more than singular plantings, according to Elm Watch and Bruce Fraedrich of Bartlett Tree Research Lab (Charlotte, NC). .... Monoculture plantings, such as alongside Pennsylvania Avenue in Washington, D.C., have disproportionate vulnerabilities to disease, and because of a poor understanding of pruning goals, uniformity of streetscape design may likely become disrupted over time along that Inauguration Day parade route due to expected failures of major structural leaders.
Based on the ratings, the preferred cultivars of American elm were 'New Harmony' and 'Princeton', and the preferred cultivars of Asian elm were TheMorton Arboretum introductions and 'New Horizon'.
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.
