European white elm

Ulmus laevis

''Ulmus laevis'' Pall., variously known as the European white elm, fluttering elm, spreading elm, stately elm and, in the USA, the Russian elm, is a large deciduous tree native to Europe, from France northeast to southern Finland, east as far as the Urals, 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. ''U. laevis'' is rare in the UK, however its random distribution, together with the absence of any record of its introduction, has led at least one British authority to consider it native.

The species was first identified, as ''Ulmus laevis'', by Pallas, in his ''Flora Rossica'' published in 1784. The tree is allogamous and is most closely related to the American elm .

Endemic to alluvial forest, ''U. laevis'' is rarely encountered at elevations above 400 m. 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 is rarely infected in western Europe.
Ulmus laevis seeds Macro,Ulmus,Ulmus laevis,seeds,trees

Appearance

''Ulmus laevis'' is similar in stature to the wych elm, if rather less symmetric, with a looser branch structure and less neatly rounded crown. It 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. The leaves are deciduous, alternate, simple ovate with a markedly lop-sided base, < 10 cm long and < 7 cm broad, comparatively thin, often almost papery in texture and very translucent, smooth above with a downy underside. The leaves are shed earlier in autumn than other species of European elm. However, 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.

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 . The species is most closely related to the American elm , from which it differs mainly in the irregular crown structure and frequent small sprout stems on the trunk and branches, features which also give the tree a distinctive winter silhouette. ''U. americana'' also has less acute leaf buds, longer petioles, narrower leaves, and a deeper apical notch in the samara which reaches the seed.

Naming

Several putative varieties have been identified. A variety ''celtidea'' from what is now the Ukraine was reported by Rogowicz in the middle of the 19th century, but no examples are known to survive. Another variety ''parvifolia'' has been reported from Serbia. 'Simplicidens' is a very rare variety, the only example known to survive is at the National Botanic Garden of Latvia in Salaspils.

Uses

The timber of the white elm is of poor quality, the cross-grain causing problems when machined, and thus of little practical use to man, not even as firewood. The density of the timber is significantly lower than that of other European elms. However, owing to its rapid growth, tolerance of soil compaction, air pollution and de-icing salts, the tree has long been used for amenity planting in towns and along roadsides.

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Taxonomy
KingdomPlantae
DivisionAngiosperms
ClassEudicots
OrderRosales
FamilyUlmaceae
GenusUlmus
SpeciesU. laevis
Photographed in
Germany