Ulmus laevis Pall., variously known as the European white elm, fluttering elm, spreading elm, stately elm and, in the United States, the Russian elm, is a large deciduous tree native to Europe, from FrancePhotographs of U. laevis (L'Orme lisse) in France: in the Forêt du Romersberg, Moselle, (bottom of page), and near Walbourg, Bas-Rhin, (top of page); Archive Krapo arboricole northeast to southern Finland, east beyond the Urals into Kyrgyzstan and Kazakhstan, and southeast to Bulgaria and the Crimea; there are also disjunct populations in the Caucasus and Spain, the latter now considered a relict population rather than an introduction by man, and possibly the origin of the European population.Fuentes-Utrilla, P., Squirrell, J., Hollingsworth, P. M. & Gil, L. (2006). Ulmus laevis (Pallas) in the Iberian Peninsula. An introduced or relict tree species? New data from cpDNA analysis. Genetics Society, Ecological Genetics Group conference, University of Wales Aberystwyth 2006. U. laevis is rare in the UK, although its random distribution, together with the absence of any record of its introduction, has led at least one British authority to consider it native.Medhurst, J. (2013). Archive for the tree detail text Category, p30. NB: The epithet 'white' elm commonly used by British foresters alluded to the timber of the wych elm.Edlin, H. L. (1947). British Woodland Trees, p.26. 3rd. edition. London: B. T. Batsford Ltd.
The species was first identified, as Ulmus laevis, by Pallas, in his Flora Rossica published in 1784.Pallas, P. S. (1784). Flora Rossica. i.75, t.48, f.F. The tree is allogamous and is most closely related to the American elm U. americana.
Endemic to alluvial forest, U. laevis is rarely encountered at elevations above 400 m.Girard, S. (2007). Dossier: L'orme: nouveaux espoirs? Forêt entreprise No. 175, Juillet 2007, Institut pour le developpement forestier, Paris. Most commonly found along rivers such as the Volga and Danube, it is one of very few elms tolerant of prolonged waterlogged, anoxic ground conditions. The species is threatened by habitat destruction and disturbance in some countries, notably Spain. Flood control schemes are particularly harmful, as seed dispersion is reliant on floods, while abstraction from aquifers lowering ground water levels has compromised the development of the trees.
Although not possessed of an innate genetic resistance to Dutch elm disease, the species was rarely infected in western Europe. However, the much warmer and drier summers of the 21st century have generated population explosions of the Scolytus bark beetles, precipitating 'feeding pressure' which has led to widescale infection of white elms in southern England and southern Netherlands. In Zeeland province.Calle, J., Calle, L., Kopinga, J., Meffert, J. (2020). Nu ook iepziekte in fladderiep. ('Now also elm disease in White Elm'). Natuur Bos Landschap, 164–168, October 2020.
Description Ulmus laevis is similar in stature to the wych elm, if rather less symmetric, with a looser, untidy, branch structure and less neatly rounded crown. The tree typically reaches a height and breadth of > 30 m, with a trunk < 2 m d.b.h. The extensive shallow root system ultimately forms distinctive high buttresses around the base of the trunk. The bark is smooth at first, then in early maturity breaks into thin grey scales, which separate with age into a network of grey-brown scales and reddish-brown underbark, and finally is deeply fissured in old age like other elms.Elwes & Henry (1913), Mitchell (1974), Phillips (1978), Bean (1981). The leaves are deciduous, alternate, simple ovate with a markedly asymmetric base, < 10 cm long and < 7 cm broad, comparatively thin, often almost papery in texture and very translucent, smooth above with a downy underside. Significantly, the leaf veins do not divide from the central vein to the leaf margin. Sheet described as U. effusa Willd.; fruit and new leaves specimen, 1840 The leaves are shed earlier in autumn than other species of European elm.
The tree is most reliably distinguished from other European elms by its long flower stems, averaging 20 mm. Moreover, the apetalous wind-pollinated flowers are distinctively cream-coloured, appearing before the leaves in early spring in clusters of 15-30; they are 3–4 mm across. The fruit is a winged samara < 15 mm long by 10 mm broad with a ciliate margin, the single round 5 mm seed maturing in late spring. The seeds have a generally high rate of germination, 45–60% for Serbian trees examined by Stilinović.Stilinović, S. (1985): Semenarstvo šumskog i ukrasnog drveća i žbunja. Univerzitet u Beogradu - Šumarski fakultet, Beograd: 1-399/Seed science of forest and decorative trees and bushes, University of Belgrade– Faculty of Forestry, Belgrade: 1-399/
Although the species is protandrous, levels of self-pollination can be high The tree can grow very rapidly; where planted in persistently moist soil, trunk width of 13-year-old trees increased by 4 cm per annum at breast height (d.b.h.).Brookes, A. H. (2020). Disease-resistant elm cultivars. Butterfly Conservation, Lulworth, England. The species differs from its closest relative, the American elm, mainly in the irregular crown structure and frequent epicormic shoots, features which also give the tree a distinctive winter silhouette. Republished 2004 Cambridge University Press, Bean, W. J. (1981). Trees and shrubs hardy in Great Britain, 7th edition. Murray, London. The American elm also has less acute leaf buds, longer petioles, narrower leaves, and a deeper apical notch in the samara which reaches the seed.Chater, A. O. (1996).'Ulmus laevis naturalized in Cards, VC46'. BSBI News 75 p.63. Botanical Society of Britain & Ireland.
Pests and diseases Like other European elms, natural populations of the European white elm have little innate resistance to Dutch elm disease. In a study in France, losses to DED amounted to 28% over a 10 year period. However, research by Irstea has isolated clones able to survive injection with the causal fungus, initially losing < 70% of their foliage, but regenerating strongly the following year.Solla et al. (2005). Screening European Elms for Resistance to Ophiostoma novo-ulmi. Forest Science, 134–141. 51 (2) 2005. Society of American Foresters.
The tree is not favoured by the vector bark beetles, which colonize it only when there are no other elm alternatives available,Collin, E., Bilger, I., Eriksson, G., & Turok, J. (2000). The conservation of elm genetic resources in Europe. In Dunn, C. P. (Ed.) (2000). The elms: breeding, conservation & disease management. Kluwer Academic Publishers, Boston. an uncommon situation in western Europe. Indeed, in a study of elm in Flanders, not one example of U. laevis was found to be afflicted by Dutch elm disease.Vander Mijnsbrugge, K., Vanden Broeck, A., & Van Slycken, J. (2005). A study of Ulmus laevis in Flanders (Northern Belgium). Belgian Journal of Botany, Vol. 138, No. 2 (2005), 199–204. Royal Botanical Society of Belgium. Research in Spain has indicated that it is the presence of an antifeedant triterpene, alnulin, at a concentration of 200 μg/g {dried bark} which renders the tree unattractive to the beetles. Ergo: the tree's decline in western Europe has been chiefly owing to woodland clearance in river valleys, and river management systems eliminating flooding, not disease. However, in 2020, it was noted by the Dutch forestry commission that many laevis, but only in Zeeland, were succumbing to Dutch elm disease for reasons unclear.
It was noted by Jouin at Metz, and a century later by Mittempergher and Santini in Italy, that U. laevis had a very low susceptibility to the elm leaf beetle Xanthogaleruca luteola. Research in Germany has established that the tree is also eschewed by the Zig Zag sawfly Aproceros leucopoda.
Elwes observed that trees planted at Ugbrooke in Devon were infested with Cacopsylla ulmi,Jerinić-Prodanović, D. (2006). A new jumping louse, Cacopsylla ulmi Förster (Homoptera, Psyllidae) on elm in Serbia. Acta entomologica serbica. 2006, 11 (1/2): 11–18. which he had never found on any other elm in Britain, an affliction confirmed many years later by Richens, who discovered the specimens of U. laevis grown at Kew were the only elms in the Gardens afflicted by the louse, and the aphid Tinocallis platani.Richens, R. H. (1983). Elm. p.64. Cambridge University Press.
The species has a slight to moderate susceptibility to elm yellows.
Cultivation U. laevis is essentially a riparian tree, able to withstand over 100 days of continual flooding,Spohn, M. (2008). Trees of Britain & Europe (Black's Nature Guides), 256 p. A & C Black, although it is intolerant of saline conditions Spanish trees were found to be calcifuge, preferring slightly acid, siliceous soils, and also drought-intolerant, their xylem vessels prone to drought-stress cavitation.Venturas, M. et al. (2013). Ulmus laevis Pall. a native elm in the Iberian peninsula: a multidisciplinary approach. Abstracts. 3rd International Elm Conference 2013. The elm after 100 years of Dutch elm disease. Florence 2013. p.48. In England, the tree failed to prosper in chalk stream valleys, where the soil was predominantly black peat, named 'Adventurers' for the Adventurers' Land SSSI in Cambridgeshire, owing to dehydration in summer. Trees planted in dry ground are notoriously short-lived.Pokorny, J. (1974). Colour Guide to Familiar Trees, Leaves, Bark and Fruit. Octopus, Czechoslovakia.
U. laevis is comparatively weak-wooded, much more so than field elm Ulmus minor, and thus an inappropriate choice for exposed locations. In trials in southern England by Butterfly Conservation, young trees of <5 m height were badly damaged by wind gusts of 40 knots (75 km/h) in midsummer storms. The species was never widely introduced to the United States, but is represented at several arboreta. Ulmus effusa, supplied by the Späth nursery of Berlin, was planted at the Dominion Arboretum, Ottawa, Canada, in 1896,Ulmus effusa at Ottawa, from Späth; New York Botanical Garden herbarium specimen 02465976, vplants.org as U. pedunculata. In the Far East, the tree has been planted in Xinjiang province and elsewhere in northern China; planting in Tongliao City is known to have been particularly successful. White elm is also known to have been introduced to Australia.Spencer, R., Hawker, J. and Lumley, P. (1991). Elms in Australia, Royal Botanic Gardens, Melbourne, Australia.
Introduction to the UK and Ireland