Ulmus pumila

Siberian elm
Siberian elms in the Gobi Desert of Mongolia
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Rosales
Family: Ulmaceae
Genus: Ulmus
Species: U. pumila
Binomial name
Ulmus pumila
L.
Synonyms
  • Ulmus campestris var. pumila Ledeb.
  • Ulmus campestris L. var. pumila (L.) Maxim.
  • Ulmus humilis Amman ex Steud.
  • Ulmus manshurica Nakai
  • Ulmus microphylla Persoon
  • Ulmus pumila var. genuina Skvort.
  • Ulmus pumila var. microphylla Persoon
  • Ulmus pumila var. transbaicalensis Pallas

Ulmus pumila, the Siberian elm, is a tree native to Central Asia, eastern Siberia, the Russian Far East, Mongolia, Tibet, northern China, India (northern Kashmir) and Korea.[1][2][3] It is also known as the Asiatic elm and dwarf elm. It is the last tree species encountered in the semi-desert regions of central Asia.[4] Described by Pallas in the 18th century from specimens from Transbaikal, Ulmus pumila has been widely cultivated throughout the Americas, Asia and, to a lesser extent, southern Europe. It is naturalized across much of the United States.[5]

Description

The Siberian elm is usually a small to medium-sized, often bushy, tree growing to 10–20 m (35–65 ft) tall, with a trunk up to 176 cm (69 1⁄4 in) d.b.h. The leaves are deciduous in cold areas, but semi-evergreen in warmer climates, less than 7 cm (2 3⁄4 in) long and less than 3 cm (1 1⁄4 in) broad, with an oblique base and a coarsely serrated margin, changing from dark green to yellow in autumn.

The perfect, apetalous wind-pollinated flowers bloom for one week in early spring, before the leaves emerge, in tight fascicles (bundles) on last year's branchlets.[2][6] Each flower is about 3 mm (1⁄8 in) across and has a green calyx with 4–5 lobes, 4–8 stamens with brownish-red anthers,[7] and a green pistil with a two-lobed style.[6][8] Unlike most elms, the Siberian elm is able to self-pollinate successfully.[9]

The wind-dispersed fruit develops in a tan-colored flat, oval samara (seed with a membraneous wing around it) 1–2 cm (3⁄8–3⁄4 in) long by 1–1.5 cm (3⁄8–5⁄8 in) wide, notched at the outer end.[2][10][11][12]

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.[13][14] A giant specimen, 45 kilometres (28 mi) southeast of Khanbogt in the south Gobi, with a girth of 5.55 m in 2009 may exceed 250 years (based on average annual ring widths of other U. pumila in the area).

Pests and diseases

The tree has considerable variability in resistance to Dutch elm disease.[15][16] 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,[17] powdery mildew, cankers,[18] aphids, and leaf spot. In the Netherlands U. pumila was also found to be susceptible to coral spot fungus Nectria cinnabarina,[19] moreover its flowers, emerging in early February, were often damaged by frost, consequently the species was dropped from the Dutch elm breeding programme.[20] In Italy, the species was also found to have a slight to moderate susceptibility to Elm Yellows.[21] However, U. pumila is the most resistant of all the elms to verticillium wilt.[22]

Cultivation and uses

A typical cultivated specimen of Ulmus pumila, Morton Arboretum
A compact form of Ulmus pumila, Groningen

U. pumila was introduced into Spain in the 16th century, and from the 1930s into Italy.[23] In these countries it has naturally hybridized with the Field Elm U. minor (see below). In Italy it was widely used in viniculture, notably in the Po valley, to support the grape vines until the 1950s, when the demands of mechanization made it unsuitable.

Three specimens were supplied by the Späth nursery of Berlin to the Royal Botanic Garden Edinburgh in 1902 as U. pumila,[24] in addition to specimens of the narrow-leaved U. pumila cultivar 'Pinnato-ramosa' (see Cultivars below).[25] One was planted in RBGE; the two not planted in the Garden may survive in Edinburgh, as it was the practice of the Garden to distribute trees about the city.[25] Kew Gardens obtained specimens of U. pumila from the Arnold Arboretum in 1908 and, as U. pekinensis, via the Veitch Nurseries in 1910 from William Purdom in northern China. [26] The popularity of U. pumila in the Great Britain has been almost exclusively as a bonsai subject, and mature trees are largely restricted to arboreta.

Introduced to the USA in 1905 by Prof. J. G. Jack,[18] and later by Meyer, the tree was initially cultivated at the USDA Experimental Station at Mandan, North Dakota, where it flourished.[27] It was consequently selected by the USDA for planting in shelter belts across 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, the species 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.

The seeds lose their viability rapidly after maturity unless placed on suitable germination conditions or dried and placed at low temperatures.[28] 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,[29] renders it vulnerable to frost damage.

As an ornamental U. pumila is a very poor tree, tending to be short-lived, with brittle wood and poor crown shape, but it has nevertheless enjoyed some popularity owing to its rapid growth and provision of shade. The Siberian Elm has been described as "one of [the world's worst], if not the world's worst trees...a poor ornamental that does not deserve to be planted anywhere".[30] Yet in the US 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.[27] A better cultivar, the Turkestan Elm, that is seen more often in gardens, and referred to as the 'wonder hedge' (Ulmus pumila celer), being both dense and fast-growing, taking as little as two years to reach fence height.

Invasiveness and spontaneous hybridization

In North America, Ulmus pumila has become an invasive species in much of the region from central Mexico [31] northward across the eastern and central United States to Ontario, Canada.[32] It also hybridizes in the wild with the native U. rubra (Slippery Elm) in the central United States.[33] In South America, the tree has spread across much of the Argentinian pampas[34][35]

In Europe it has spread widely in Spain, and hybridizes extensively there with the native field elm (U. minor), contributing to conservation concerns for the latter species.[36][37] Research is ongoing into the extent of hybridisation with U. minor in Italy.[38]

Ulmus pumila is often 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; 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,[39][40] as well as along transportation corridors.

The species is now listed in Japan as an alien species recognized as established in Japan or found in the Japanese wild.[41]

Varieties

Two varieties were traditionally recognized: var. pumila and var. arborea, the latter also being known as U. pinnato-ramosa, the cultivar 'Turkestan'.

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 United States and Italy to create robust trees of more native appearance with high levels of resistance to Dutch elm disease:

Notable trees

Roerich describes a specimen discovered on his travels through Mongolia:

We are in the deserts of Mongolia. It was hot and dusty yesterday. From faraway thunder was approaching. Some of our friends became tired from climbing the stony holy hills of Shiret Obo. While already returning to the camp, we noticed in the distance a huge elm tree – ‘karagatch’, - lonely, towering amidst the surrounding endless desert. The size of the tree, its somewhat familiar outlines attracted us into its shadow. Botanical considerations led us to believe that in the wide shade of the giant there might be some interesting herbs. Soon, all the co-workers gathered around the two mighty stems of the karagatch. The deep, deep shadow of the tree covered about 50 feet across. The powerful tree-stems were covered with fantastic burr growths. In the rich foliage, birds were singing and the beautiful branches were stretched out in all directions, as if wishing to give shelter to all pilgrims.[42]

The USA National Champion, measuring 33.5 m (109 ft 11 in) high in 2011, grows in Berrien County, Michigan.[43] In the UK the TROBI Champions grow at Thorp Perrow Arboretum, Yorkshire, (19 m, 62 ft × 70 cm, 28 inches in 2004), and at St Anne's Well Gardens, Hove, Sussex (20 m, 66 ft × 60 cm, 24 inches in 2009).[44]

Accessions

North America
Europe
Australasia

References

Wikimedia Commons has media related to Ulmus pumila.
  1. ↑ 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.
  2. 1 2 3 "Ulmus pumila". Flora of China. Missouri Botanical Garden – via eFloras.org.
  3. ↑ "Ulmus pumila". Germplasm Resources Information Network (GRIN). Retrieved 8 September 2016.
  4. ↑ onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2005.01384.x/pdf
  5. ↑ "Ulmus pumila". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2013.
  6. 1 2 "Ulmus pumila". Flora of North America (FNA). Missouri Botanical Garden – via eFloras.org.
  7. ↑ Hilty, John (2016). "Siberian Elm (Ulmus pumila)". Illinois Wildflowers.
  8. ↑ "Ulmus". Flora of North America (FNA). Missouri Botanical Garden – via eFloras.org.
  9. ↑ Townsend, A. M. (1975). "Crossability patterns and morphological variation among elm species and hybrids". 24 (1). Sylvae Genetica: 18–23.
  10. ↑ Elwes, H. J. & Henry, A. (1913). The Trees of Great Britain & Ireland. Vol. VII. 1848–1929. Republished 2004 Cambridge University Press, ISBN 978-1-108-06938-0
  11. ↑ Rushforth, K (1999). Trees. Collins.
  12. ↑ Huxley, A. (1992). The New RHS Dictionary of Gardening. Macmillan.
  13. ↑
  14. ↑ "Pictures".
  15. ↑ Smalley, E. & Guries, R. P. (1993). "Breeding elms for resistance to Dutch elm disease". 31. Annual Review of Phytopathology: 25–352.
  16. ↑ Zalapa, J. E., Brunet, J., & Guries, R. P (2008). "Genetic diversity and relationships among Dutch elm disease tolerant Ulmus pumila L. accessions from China". NRC Research Press Web. USA: Genome. 51: 492–500.
  17. ↑ Miller, F. & Ware, G. (2001). "Resistance of Temperate Chinese Elms (Ulmuss spp.) to Feeding of the Adult Elm Leaf Beetle (Coleoptera: Chrysomelidae)". Journal of Economic Entomology. Entom. Soc.of America. 94 (1): 162–166. doi:10.1603/0022-0493-94.1.162.
  18. 1 2 Leopold, D. J. (1980). Chinese and Siberian elms. Journal of Arboriculture. 6 (7): July 1980, 175–179
  19. ↑ Heybroek, H. M. (1957). "Elm breeding in the Netherlands". 6 (3-4). Silvae Genetica: 112–117.
  20. ↑ Went, J. (1954). The Dutch Elm Disease – Summary of fifteen years' hybridization and selection work (1937–1952). European Journal of Plant Pathology. 02(1954); 60(2): 109–1276.
  21. ↑ Mittempergher, L. & Santini, A. (2004). The History of Elm Breeding. Invest. Agrar.: Sist Recur For. 2004 13 (1), 161-177.
  22. ↑ Pegg, G. F. & Brady, B. L. (2002). Verticillium Wilts. CABI Publishing. ISBN 0-85199-529-2.
  23. ↑ "Hybridization and introgression between the exotic Siberian elm, Ulmus pumila, and the native Field elm, U. minor, in Italy". Biological Invasions. 15: 2717–2730. doi:10.1007/s10530-013-0486-z.
  24. ↑ U. pumila herbarium leaf-specimens, RBGE 1902: elmer.rbge.org
  25. 1 2 Accessions book. Royal Botanic Garden Edinburgh. 1902. pp. 45,47.
  26. ↑ Elwes and Henry (1913), p.1927
  27. 1 2 Klingaman, G. (1999). Plant of the Week: Siberian Elm. Extension News, University of Arkansas, Division of Agriculture.
  28. ↑ Hirsch, H., Wypior, C., Wehrden, H., Wesche, K., Renison, D, and Hensen, I. (2012). Germination performance of native and non-native Ulmus pumila populations. Neobiota 15, 53–68. 14 Dec. 2012.
  29. ↑ Geng, M. A. (1989). A provenance test with elm (Ulmus pumila L.) in China. 32. Silvae Genetica. pp. 37–44.
  30. ↑ Dirr, M. (1975). "Manual of Woody Landscape Plants". Champaign, Illinois: Stipes Publishing LLC.
  31. ↑ Todzia, C. A. & Panero, J. L. (1998). "A new species of Ulmus (Ulmaceae) from southern Mexico and a synopsis of the species in Mexico". 50 (3). Brittonia: 346. JSTOR 2807778.
  32. ↑ McIlvain, E. H. & Armstrong, C. G. (1965). Siberian Elm: A Tough New Invader of Grasslands. Weeds, Vol. 13, No. 3 (July 1965), pp 278 – 279. Weed Science Society of America & Allen Press.
  33. ↑ J. E. Zalapa; J. Brunet; R. P. Guries (June 28, 2008). "Isolation and characterization of microsatellite markers for red elm (Ulmus rubra Muhl.) and cross-species amplification with Siberian elm (Ulmus pumila L.)". Mol Ecol Resour. Wiley Online Library. 8 (1): 109–12. doi:10.1111/j.1471-8286.2007.01805.x. PMID 21585729.
  34. ↑ Villamil, C. B., Zalba, S. M. Red de información sobre especies exóticas invasoras – I3N-Argentina Universidad Nacional del Sur Bahía Blanca, Argentina.
  35. ↑ Hiersch, H., Hensen, I., Zalapa, J. Guries, R. & Brunet, J. (2013). Is hybridization a necessary condition for the evolution of invasiveness in non-native Siberian elm? Abstracts. Third International Elm Conference 2013. The elm after 100 years of Dutch elm disease. Florence, p45.
  36. ↑ Cogolludo-Agustín, Miguel Ángel; Agúndez, Dolores; Gil, Luis (1 August 2000). "Identification of native and hybrid elms in Spain using isozyme gene markers". Heredity. 85 (2): 157–166. doi:10.1046/j.1365-2540.2000.00740.x – via www.nature.com.
  37. ↑ Cogolludo-Agustín, Miguel ángel; Agúndez, Dolores; Gil, Luis. "Identification of native and hybrid elms in Spain using isozyme gene markers". 85 (2): 157–166. doi:10.1046/j.1365-2540.2000.00740.x.
  38. ↑ Brunet, Johanne; Zalapa, Juan E.; Pecori, Francesco; Santini, Alberto (14 May 2013). "Hybridization and introgression between the exotic Siberian elm, Ulmus pumila, and the native Field elm, U. minor, in Italy". Biol Invasions. 15 (12): 2717–2730. doi:10.1007/s10530-013-0486-z – via link.springer.com.
  39. ↑ National Audubon Society (2002). Field Guide to North American Trees, Western Region, p. 419-420
  40. ↑ (http://www.hear.org/pier/), Pacific Island Ecosystems at Risk project (PIER). "Ulmus pumila (PIER species info)".
  41. ↑
  42. ↑ de Roerich, G. (1931). Trails to Inmost Asia. Yale University Press.
  43. ↑ American Forests. (2012). The 2012 National Register of Big Trees.
  44. ↑ Johnson, O. (ed.). (2011). Champion Trees of Britain & Ireland. Royal Botanic Gardens, Kew, London. ISBN 978-1-84246-452-6
  45. ↑ "List of plants in the {elm} collection". Brighton & Hove City Council. Retrieved 23 September 2016.
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