Siberian Elm

Ulmus pumila L., the Siberian Elm, is native to Turkestan, eastern Siberia, Mongolia, Xizang (Tibet), northern China, India (northern Kashmir) and Korea ^[1]. It is also known as the Asiatic Elm, Dwarf Elm and (erroneously) Chinese Elm. The tree has also been widely cultivated throughout Asia, North America and, to a lesser extent, southern Europe. It is usually a small to medium-sized, often bushy, tree growing to 10 - 20 m tall, with a trunk up to 80 cm d.b.h. The leaves are deciduous in cold areas, but semi-evergreen in warmer climates, < 7 cm long and < 3 cm broad, with an oblique base and a coarsely serrated margin, changing from dark green to yellow in autumn. The wind-dispersed fruit develops in a flat, oval membranous wing (:samara) 1 - 1.5 cm long and notched at the outer end ^[2] ^[3] ^[4]. The tree is shortlived in temperate climates, rarely reaching more than 60 years of age, but in its native environment may live to between 100 and 150 years [3].

Ecology

The Siberian elm has a high sunlight requirement and is not shade-tolerant. With adequate light it exhibits rapid growth. It is also fairly intolerant of wet ground conditions, growing better on well-drained soils. The species shows considerable variability in Dutch elm disease resistance ^[5]. While is very resistant to drought and severe cold, and able to grow on poor soils, its short period of dormancy, flowering early in spring followed by continuous growth until the first frosts of autumn, ^[6] renders it vulnerable to frost damage. Moreover, like many other elms in North America it is highly susceptible to damage from many insects and parasites, including the elm leaf beetle, powdery mildew, cankers, aphids, and leaf spot. However, it is the most resistant of all the elms to verticillium wilt ^[7].

In North America it has become an invasive species from Utah east to Kansas and north to Ontario. It is found in abundance along railroads and in abandoned lots and on disturbed ground. The gravel along railroad beds provides ideal conditions for its growth: well-drained, nutrient poor soil, and high light conditions, and these beds provide corridors which facilitate its spread. Owing to its high sunlight requirements, it seldom invades mature forests, and is primarily a problem in cities and open areas ^[8].

Cultivation and uses

U. pumila was introduced to North America by Frank Meyer [4], who whilst in the employ of the USDA made several collecting expeditions to the Far East. The tree was initially cultivated at the USDA Experimental Station at Mandan, North Dakota, where it flourished ^[10]. It was consequently selected by the USDA for planting in shelter belts acoss the prairies in the aftermath of the Dustbowl disasters, where its rapid growth and tolerance for drought and cold initially made it a great success, however it later proved susceptible to numerous maladies. Attempts to find a more suitable cultivar were initiated in 1997 by the Plant Materials Center of the USDA, which established experimental plantations at Akron, Colorado and Sidney, Nebraska. The study, no. 201041K, will conclude in 2020.

As an ornamental it is a very poor tree, tending to be short-lived, with brittle wood and poor crown shape, but has nevertheless enjoyed some popularity owing to its rapid growth and provision of shade. The Siberian Elm has been described by Prof. Michael Dirr as "one of, if not the, world's worst trees...a poor ornamental that does not deserve to be planted anywhere" ^[11]. Yet in the USA during the 1950s, the tree was also widely promoted as a fast growing hedging substitute for Privet, and as a consequence is now commonly found in nearly all states ^[10]. In the UK, its popularity has been almost exclusively as a bonsai subject, and mature trees are largely restricted to arboreta. Introduced into Spain in the 16th century, and later Italy, it has naturally hybridized with the Field Elm U. minor. In Italy it was widely used in viniculture, notably in the Po valley, to support vines until the 1950s, when the demands of mechanization made it unsuitable.

Subpecies & varieties

Cultivars

Valued for the high resistance of some clones to Dutch elm disease, over a dozen selections have been made to produce hardy ornamental cultivars, although several may no longer be in cultivation:

Hybrid cultivars

The species has been widely hybridized in the USA and Italy to create robust trees of more native appearance with high levels of resistance to Dutch elm disease:

Also U. '260' (Ulmus × hollandica 'Vegeta' × Ulmus pumila) raised at Wageningen but never commercially released; a few specimens survive as part of the Brighton & Hove CC NCCPG Elm Collection at Happy Valley Park, Woodingdean; Crespin Way, Hollingdean (10 trees), The Highway, Moulsecoomb (1 tree) and Royal Pavilion Gardens (1 tree).

Arboreta etc accessions

Nurseries

Seed suppliers

References

^ Fu, L., Xin, Y. & Whittemore, A. (2002). Ulmaceae, in Wu, Z. & Raven, P. (eds) Flora of China, Vol. 5 (Ulmaceae through Basellaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis, USA. [1]
^ Elwes, H. J. & Henry, A. (1913). The Trees of Great Britain & Ireland. Vol. VII. pp 1848–1929. Private publication. [2]
^ Rushforth, K. (1999). Trees. Collins.
^ Huxley, A. (1992). The New RHS Dictionary of Gardening. Macmillan.
^ Smalley, E. & Guries, R. P. (1993). Breeding elms for resistance to Dutch elm disease. Annual Review of Phytopathology, 31, 325-352
^ Geng, M. A. (1989). A provenance test with elm (Ulmus pumila L.) in China. Silvae Genetica 32 (2), 37-44.
^ Pegg, G. F. & Brady, B. L. (2002). Verticillium Wilts. CABI Publishing. ISBN 0851995292
^ National Audubon Society (2002). Field Guide to North American Trees, Western Region, p. 419-420
^ Villamil, C. B., Zalba, S. M. Red de información sobre especies exóticas invasoras - I3N-Argentina Universidad Nacional del Sur Bahía Blanca, Argentina
^ ^a ^b Klingaman, G. (1999). Plant of the Week: Siberian Elm. Extension News, University of Arkansas, Division of Agriculture.
^ Dirr, M. (1975). Manual of Woody Landscape Plants. Stipes Publishing LLC. Champaign, Illinois.
^ Johnson, Owen (ed.) (2003). Champion Trees of Britain & Ireland. Whittet Press, ISBN 9781873580615.

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