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'' 'Ascendens', 'Upright American Elm', was cloned c.1910 by Bernard H. Slavin, Superintendent of Parks,

Rochester Rochester may refer to: Places Australia * Rochester, Victoria Canada * Rochester, Alberta United Kingdom *Rochester, Kent ** City of Rochester-upon-Medway (1982–1998), district council area ** History of Rochester, Kent ** HM Prison ...

, New York, from a tree growing in

Seneca Park Seneca Park was the last park designed by Frederick Law Olmsted's Olmsted Brothers, firm in Louisville, Kentucky, United States. The park system in Louisville was the last of five designed by the Olmsted firm. The park resides in the Louisville ne ...

, Rochester, and named in 1927 for its narrow oval form.Malcolm A. Milne & Jacob Gerling, 'Improved elm is upright form', ''Trees Magazine'', September-October 1941, Vol.4, No.5, p.9; Santa Monica, California
/ref> See also the similar cultivars 'Columnaris' and 'Augustine Ascending'. It is not known why such a promising clone as 'Ascendens' appears rare in cultivation, but 'Augustine Ascending' was released at about the same date. Neither

Green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combi ...

nor Santamour suggested that they were synonyms.

Description

The tree has small, fastigiate lateral branches forming a narrow, oval head. Its leaves are similar in shape and texture to those of the parent species, but slightly smaller. Arnold Arboretum, however, report leaves 3 to 6 in. long and 2 to 4 in. wide. The bark remains smooth for longer than usual in the species and its fissures are less deep, while the trunk lacks the marked buttressing of the species.

Pests and diseases

The clone's 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 ...

is not known, but the species is highly susceptible to the disease and

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 ...

; it is also moderately preferred for feeding and reproduction by the adult 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 ...

'', and highly preferred for feeding by the Japanese Beetle '' Popillia japonica'' in the United States. ''U. americana'' is also 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.

Cultivation

In an article on the cultivar, ''Trees Magazine'' (Sept.-Oct. 1941), observing of American elm that there were "too many city streets where sidewalks are upheaved by its heavily buttressed trunk, lawns impaired by its massed tops, and roofs overhung by upper branches brushing the gables of homes," described 'Ascendens' as, by contrast, "an ideal variety for the narrow streets of our cities and for small-area planting". The tree was much planted in the Rochester area. It was described as hardy and less prone to wind-damage than broader forms. The tree is not known to have been cultivated beyond the US.

Accessions

North America

Arnold Arboretum, US. Acc. no. 140-61.

References

{{Elm species, varieties, hybrids, hybrid cultivars and species cultivars , state=collapsed American elm cultivar Ulmus articles missing images Ulmus