European White Elm
The European White Elm, yclept Fluttering Elm, Spreading Elm and, in the USA, 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 is also a disjunct population in the Caucasus. Moreover, a small number of trees found in Spain is now considered a relict population rather than an introduction by man, and possibly the origin of the European population.
Essentially endemic to alluvial forest, it 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 White Elm is allogamous and is most closely related to the American Elm.
The tree 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 leaves are deciuous, alternate, simple ovate with a lop-sided base, < 10 cm long and < 7 cm broad, comparatively thin, often almost papery in texture and very translucent, with a downy underside. The apetalous wind-pollinated flowers appear before the leaves in early spring, produced in clusters of 15-30; they are 3-4 mm across on 20 mm long stems. 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. In England, trees grown from seed commenced flowering in their 12th year.
The tree is most reliably distinguished from other European elms by the long flower stems, and is most closely related to the American Elm, from which it differs mainly in the irregular crown shape and frequent small sprout stems on the trunk.