|Ulmus pumila subsp. var.||Chinese elm, Siberian Elm|
Ulmus pumila L., the Siberian Elm, is native to Turkestan, eastern Siberia, Mongolia, Xizang (Tibet), northern China, India (northern Kashmir) and Korea . It is also known as the Asiatic Elm, Dwarf Elm and (erroneously) Chinese Elm. U. pumila has been widely cultivated throughout Asia, North America and, to a lesser extent, southern Europe.
The Siberian Elm 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   . The tree is short-lived in temperate climates, rarely reaching more than 60 years of age, but in its native environment may live to between 100 and 150 years .
|Standard Cyclopedia of Horticulture|
Ulmus pumila, Linn. (U. microphylla, Pers. U. sibirica, Hort.). Small tree or shrub, with slender pubescent, sometimes pendulous branches: lvs. oval-elliptic to elliptic-lanceolate, short-petioled, acute, firm, dark green and smooth above, pubescent when young beneath, 3/4 - 3 in. long: fls. short-pedicelled; stamens 4-5, with violet anthers: fr. obovate, with the nutlet somewhat above the middle, incision at the apex reaching about half-way to the nutlet. Turkestan to Siberia and N. China.—A graceful small hardy tree. Var. arborea, Litwinow (U. pinnata-ramosa, Dieck. U. turkestanica, Regel). Tree with long, pinnately branched shoots pubescent when young: lvs. oblong-lanceolate, 1 – 2 1/2 in. long; petioles pubescent at first. Var. pendula, Hort. (U. parvifolia pendula, Hort. Planera repens, Hort.), has slender more pendulous branches. CH
As an ornamental U. pumila 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" . 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 . 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.
In North America it has become an invasive species from central Mexico   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 . In South America, the tree has spread across much of the Argentinian pampas .
The species has a high sunlight requirement and is not shade-tolerant; with adequate light it exhibits rapid growth. The tree is also fairly intolerant of wet ground conditions, growing better on well-drained soils. While it 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,  renders it vulnerable to frost damage.
Pests and diseases
The tree has considerable variability in resistance to Dutch elm disease. Moreover, like many other elms in North America, it is highly susceptible to damage from many insects and parasites, including the elm leaf beetle Xanthogaleruca luteola, powdery mildew, cankers, aphids, and leaf spot. In trials in Italy, the species was also found to have a slight to moderate susceptibility to Elm Yellows. However, U. pumila is the most resistant of all the elms to verticillium wilt.
One variety is recognized: var. arborea Litv..
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:
- Ansaloni, Aurescens, Chinkota, Dropmore, Green King, Hansen, Harbin, Manchu, Mr. Buzz, Park Royal, Pendula, Pyramidalis Fiorei, Variegata
- Arno, Cathedral, Coolshade, Fiorente, Homestead, Lincoln, Morton Plainsman, Morton Stalwart, New Horizon, Plinio, Regal, Rosehill, San Zanobi, Urban, Willis.
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).
- ↑ 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. 
- ↑ Elwes, H. J. & Henry, A. (1913). The Trees of Great Britain & Ireland. Vol. VII. pp 1848–1929. Private publication. 
- ↑ Rushforth, K. (1999). Trees. Collins.
- ↑ Huxley, A. (1992). The New RHS Dictionary of Gardening. Macmillan.
- ↑ Dirr, M. (1975). Manual of Woody Landscape Plants. Stipes Publishing LLC. Champaign, Illinois.
- ↑ Klingaman, G. (1999). Plant of the Week: Siberian Elm. Extension News, University of Arkansas, Division of Agriculture.
- ↑ Todzia, C. A. & Panero, J. L. (2006). A new species of Ulmus (Ulmaceae) from southern Mexico and a synopsis of the species in Mexico. Brittonia, Vol 50, (3): 346
- ↑ 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
- ↑ Geng, M. A. (1989). A provenance test with elm (Ulmus pumila L.) in China. Silvae Genetica 32 (2), 37-44.
- ↑ Smalley, E. & Guries, R. P. (1993). Breeding elms for resistance to Dutch elm disease. Annual Review of Phytopathology, 31, 325-352
- ↑ Miller, F. and Ware, G. (2001). Resistance of Temperate Chinese Elms (Ulmuss spp.) to Feeding of the Adult Elm Leaf Beetle (Coleoptera: Chrysomelidae). Journal of Economic Entomology 94 (1): 162-166. 2001. Entom. Soc.of America.
- ↑ 
- ↑ Mittempergher, L. & Santini, A. (2004). The History of Elm Breeding. Invest. Agrar.: Sist Recur For. 2004 13 (1), 161-177.
- ↑ Pegg, G. F. & Brady, B. L. (2002). Verticillium Wilts. CABI Publishing. ISBN 0-85199-529-2