Black poplar is a fast-growing Eurasian tree, which can reach 40 metres in height. It has a native distribution extending from Ireland in the west to Kazakhstan and western China in the east and from northern Russia to North Africa in the south. As a deciduous, pioneer species, it is intolerant of shade and drought, and is found in lowland floodplain forests and on the margins of watercourses.
Black poplar is dioecious, with separate male and female plants, producing flowers before the leaves. Catkins of male flowers produce abundant yellow, wind-dispersed pollen. Catkins of female flowers produce capsules filled with hairy, wind-dispersed seeds.
Morphological variation of black poplar across its vast geographic range has been divided among numerous subspecies, varieties, and cultivars. Understanding patterns of variation are complicated by the hybridisation of black poplar with other poplar species, and the widespread selection and planting of black poplar clones for horticultural and forestry purposes. In Europe, at least three native subspecies are recognised: ssp. nigra in central and eastern Europe; ssp. betulifolia in north-west Europe; and ssp. caudina in the Mediterranean.
In the United Kingdom, ssp. betulifolia is native, but sparsely scattered, south of a line joining the watersheds of the Humber in the east and the Mersey in the west. However, this subspecies was not originally described from Britain; the type specimen was collected in the Hudson Valley, New York, at the turn of the nineteenth century by the French botanist François André Michaux (1770-1855). It was thought to be native to North America, but is now known to have been introduced from Europe.
Much more familiar in the United Kingdom are introduced forms of black poplar of which the most immediately recognisable is the slender, flame-shaped, exclusively male, Lombardy poplar (cultivar ‘Italica’). This fastigiate mutation appears to have arisen in the Po Valley at the turn of the eighteenth century and was propagated as cuttings. It was introduced to France in 1749 and then into Britain about 1758, from Turin, by the Anglo-Dutch diplomat William Nassau de Zuylestein (1717-81), Earl of Rochford. However, most trees grown as Lombardy poplar in Britain are hybrids between true Lombardy poplar and ssp. betulifolia; they belong to cultivar ‘Plantierensis’. These trees are a mixture and male and female clones. In the north west of England, a male black poplar cultivar, called ‘Manchester’, was widely planted because it is highly resistant to air pollution.
Cooper F 2006. The black poplar: ecology, history and conservation. Windgather Press.
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Milne-Redhead E 1990. The BSBI Black Poplar survey, 1973-88. Watsonia 18: 1-5.