Ulmus americana 'Princeton' | |
---|---|
Species | Ulmus americana |
Cultivar | 'Princeton' |
Marketing names | Princeton American Elm |
Origin | Princeton Nurseries |
The American Elm cultivar Ulmus americana 'Princeton' was originally selected in 1922 by New Jersey nurseryman William Flemer of Princeton Nurseries for its aesthetic merit. 'Princeton' was later found to have a moderate resistance to Dutch elm disease (DED). [1] [2] [3]
American elm is a vase-shaped, medium to large, deciduous tree. [4] The tree can grow to greater than 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 later lead to branch breakages. The leaves are less than 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. [5] The tree commences flowering aged nine years.
Testing in laboratory conditions by the United States Department of Agriculture (USDA) from 1992 to 1993 revealed that 'Princeton' had some resistance to Dutch elm disease (DED), [6] [7] [8] 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 percent dieback, attributed by some accounts to Dutch Elm Disease. [9] A 2016 publication later reported that, of 100 Princeton elms planted from 2001 to 2007 within a three state area in the United States, nine came down with DED, seven died, and two were saved by assiduous pruning. [2]
Moreover, trees introduced to the United Kingdom, where the larger bark beetle Scolytus scolytus is the principal vector, were found to be susceptible, and many died, as did all 20 sent to Eisele, Darmstadt, for testing by inoculation with the pathogen. [10] Princeton elms planted in North America are highly prone to leaf damage by Japanese beetles Popillia japonica . [11] 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. [12] Trees grown in northern California at UC Davis became infested with leaf curling aphids ( Eriosoma ), producing copious amounts of honeydew. [5]
Regular pruning and spraying is advisable because of Dutch elm disease. [4] The preferred cultivars of the American elm ( Ulmus americana ) for resistance to DED are 'New Harmony' and 'Princeton' as determined by the National (American) Elm Trial. [5] [13]
It can be grown in USDA zones 4 through 9, [4] in "...average, medium moisture, well-drained soils in full sun. [It is t]olerant of light shade [and p]refers rich, moist loams [adapting] to both wet and dry sites. [It is g]enerally tolerant of urban conditions." [4]
Examples of 'Princeton' were planted along Washington Road and another road in Princeton; most of these trees survive to this day unaffected by disease. [15] In 2005, approximately 90 Princeton elms were planted along Pennsylvania Avenue in front of the White House in Washington, D.C. [16] 'Princeton' is currently being evaluated in the United States as part of the National Elm Trial coordinated by Colorado State University. [17]
The tree was introduced to the UK by Penelope Hobhouse, who obtained two specimens from the New York Botanical Gardens for planting at her family home, Hadspen, in Somerset. The tree was later marketed by the Knoll Gardens nursery in Dorset. In 2005, 50 'Princeton' were planted by The Prince of Wales to create the Anniversary Avenue at his residence Highgrove House, however all the trees were removed and burnt in 2012 after five died of DED. [10] In Ireland, 100 were planted in Phoenix Park, Dublin, in 2009 to replace some of the 2000 native elms lost to Dutch elm disease since the 1980s. [18] In Scotland, some six have been planted in Edinburgh parks (Gayfield Square Park, The Meadows, Leith Links). [19]
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 Florida and central Texas, and is the State Tree of Massachusetts. The American elm is an extremely hardy tree that can withstand winter temperatures as low as −42 °C. Trees in areas unaffected by Dutch elm disease (DED) can live for several hundred years. A prime example of the species was the Sauble Elm, which grew beside the banks of the Sauble River in Ontario, Canada, to a height of 43 m (140 ft), with a d.b.h of 196 cm (6.43 ft) before succumbing to DED; when it was felled in 1968, a tree-ring count established that it had germinated in 1701.
Ulmus 'San Zanobi' is a hybrid elm cultivar raised by the Istituto per la Protezione delle Piante (IPP) in Florence, from a crossing of the Dutch hybrid 'Plantyn' and the Siberian Elm Ulmus pumila clone 'S 15'; it was released to commerce in 2002. 'San Zanobi' was introduced to the UK in 2004 by Hampshire & Isle of Wight Branch, Butterfly Conservation, as part of its assessment of DED-resistant cultivars as potential hosts of the endangered White-letter Hairstreak.
Ulmus laciniata(Trautv.) Mayr, known variously as the Manchurian, cut-leaf, or lobed elm, is a deciduous tree native to the humid ravine forests of Japan, Korea, northern China, eastern Siberia and Sakhalin, growing alongside Cercidiphyllum japonicum, Aesculus turbinata, and Pterocarya rhoifolia, at elevations of 700–2200 m, though sometimes lower in more northern latitudes, notably in Hokkaido.
Ulmus 'Frontier' is an American hybrid cultivar, a United States National Arboretum introduction derived from a crossing of the European Field Elm Ulmus minor with the Chinese Elm Ulmus parvifolia in 1971. Released in 1990, the tree is a rare example of the hybridization of spring- and autumn-flowering elms. Tested in the US National Elm Trial coordinated by Colorado State University, 'Frontier' averaged a survival rate of 74% after 10 years.
Ulmus 'Homestead' is an American hybrid elm cultivar raised by Alden Townsend of the United States National Arboretum at the Nursery Crops Laboratory in Delaware, Ohio. The cultivar arose from a 1970 crossing of the Siberian Elm Ulmus pumila with the hybrid N 215, the latter grown from seed sent in 1960 to the University of Wisconsin-Madison elm breeding team by Hans Heybroek of the De Dorschkamp Research Institute in the Netherlands. Tested in the US National Elm Trial coordinated by Colorado State University, 'Homestead' averaged a survival rate of 85% after 10 years. 'Homestead' was released to commerce without patent restrictions in 1984.
The hybrid elm cultivar Ulmus × hollandica 'Pioneer' is an American clone arising from the crossing of two European species, Wych Elm U. glabra and Field Elm U. minor. Raised by the USDA station at Delaware, Ohio, in 1971, 'Pioneer' was released to commerce in 1983.
Ulmus 'Morton' is an elm cultivar cloned from a putative intraspecific hybrid planted at the Morton Arboretum in 1924, which itself originated as seed collected from a tree at the Arnold Arboretum in Massachusetts. Although this tree was originally identified as Ulmus crassifolia, it is now believed to have been a hybrid of the Japanese elm and Wilson's elm. Accolade has proven to be the most successful cultivar tested in the US National Elm Trial, averaging a survival rate of 92.5% overall.
Ulmus 'Morton Glossy' is a hybrid cultivar raised by the Morton Arboretum, Illinois. Originally named 'Charisma' until it was realized that name had already been registered for another plant, the tree was derived from a crossing of two other hybrid cultivars grown at the Morton: Accolade and Vanguard. Tested in the US National Elm Trial coordinated by Colorado State University, Triumph averaged a survival rate of 86% after 10 years. Triumph was introduced to the UK in 2006 by the Frank P. Matthews nursery in Worcestershire.
Ulmus 'Morton Plainsman' is a hybrid cultivar raised by the Morton Arboretum from a crossing of Siberian Elm and a Japanese Elm grown from openly pollinated seed donated by the Agriculture Canada Research Station at Morden, Manitoba. Tested in the US National Elm Trial coordinated by Colorado State University, Vanguard averaged a survival rate of 78% after 10 years.
Ulmus 'Morton Stalwart', is a Morton Arboretum hybrid cultivar arising from a controlled crossing of Accolade with the hybrid of a Field Elm U. minor from eastern Russia and a Siberian Elm U. pumila. Tested in the US National Elm Trial coordinated by Colorado State University, Commendation averaged a survival rate of 85% after 10 years.
The Siberian elm cultivar Ulmus pumila 'Green King' was once believed to have been derived from a crossing of the Siberian Elm Ulmus pumila with the American Red Elm Ulmus rubra. However, it is now apparent the tree originated as a sport of U. pumila in 1939 at the Neosho Nurseries, Neosho, Missouri.
The American elm cultivar Ulmus americana 'Augustine', originally called 'Augustine Ascending', was cloned by Archie M. Augustine of the Augustine Nursery of Bloomington, Illinois, from a nursery seedling planted in 1927 in Normal, Illinois, and found to be columnar in habit.
The American Elm cultivar Ulmus americana 'Delaware' was originally selected from 35,000 seedlings inoculated with the Dutch elm disease fungus in USDA trials at Morristown, New Jersey.
The American Elm cultivar Ulmus americana 'Valley Forge' was raised by the Agricultural Research Service in Maryland. 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. '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.
The American elm cultivar Ulmus americana 'New Harmony' was raised by the Maryland Agricultural Research Service and released by the United States National Arboretum in 1995, along with 'Valley Forge'. 'New Harmony' proved the most successful U. americana cultivar in the US National Elm Trial, averaging a survival rate of 85.5% overall.
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 on the National Mall in Washington, D.C. 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).
The American elm cultivar Ulmus americana 'American Liberty' is in fact a group of six genetically distinct cultivars under a single name, although they are superficially similar. The Liberty elm is reportedly suitable for street planting, being tolerant of de-icing salts and air pollution. However, examples included in 10-year trials at Atherton, California to evaluate replacements for Californian elms lost to disease did not perform well. The late Professor Eugene Smalley summarized 'American Liberty' as "not as resistant as the Asian hybrids, but it still has the look of a classic American Elm".
The Japanese elm cultivar Ulmus davidianavar.japonica 'Prospector' was originally treated as a cultivar of Wilson's elm U. wilsonianaSchneid., a species sunk as Ulmus davidiana var. japonica by Fu. A U.S. National Arboretum introduction, it was selected in 1975 from a batch of 1965 seedlings in Delaware, Ohio, and released without patent restrictions in 1990. 'Prospector' proved moderately successful in the US National Elm Trial, averaging a survival rate of 76% overall.
Ulmus 'Patriot' is a hybrid cultivar raised by the United States National Arboretum in 1980. Derived from a crossing of the American hybrid 'Urban' with the Wilson's Elm cultivar 'Prospector', 'Patriot' was released to commerce, free of patent restrictions, in 1993. Tested in the US National Elm Trial coordinated by Colorado State University, 'Patriot' averaged a survival rate of 85% after 10 years.
Ulmus 'Fiorente' is a hybrid cultivar elm derived from a crossing of the Siberian Elm Ulmus pumila clone 'S.10' from Lucca, Italy, with the Ulmus minor clone 'C.02' from Lungarno, Florence, by the Istituto per la Protezione delle Piante (IPP), part of the Italian National Research Council, in Florence. The tree is protected by Plant Breeders' Rights bestowed by the EU on 25 March 2010.
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