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''Populus nigra'', the black poplar, is a species of cottonwood poplar, the type species of section ''Aigeiros'' of the genus ''Populus'', native to Europe, southwest and central Asia, and northwest Africa.〔Flora Europaea: (''Populus nigra'' )〕 It is a medium-sized to large deciduous tree, reaching 20–30 m (rarely 40 m) tall, with a trunk up to 1.5 m diameter, though some old individuals have grown much bigger (more than 3 meters DBH for several trees in France). The leaves are diamond-shaped to triangular, 5–8 cm long and 6–8 cm broad, green on both surfaces.〔Rushforth, K. (1999). ''Trees of Britain and Europe''. Collins ISBN 0-00-220013-9.〕 The species is dioecious (male and female flowers on different plants), with flowers in catkins and pollination by wind. The black poplar grows in low-lying areas of moist ground.〔(【引用サイトリンク】url=https://www.woodlandtrust.org.uk/learn/british-trees/native-trees/black-poplar/ )〕 There are three subspecies, some botanists distinguishing a fourth:〔〔 *''Populus nigra'' subsp. ''nigra''. Central and eastern Europe. Leaves and shoots glabrous (hairless); bark grey-brown, thick and furrowed. *''Populus nigra'' subsp. ''betulifolia'' (Pursh) W.Wettst. North-west Europe (France, Great Britain, Ireland). Leaf veins and shoots finely downy; bark grey-brown, thick and furrowed, often with heavy burrs, trunk usually heavily leaning. *''Populus nigra'' subsp. ''caudina'' (Ten.) Bugała. Mediterranean region, also southwest Asia if var. ''afghanica'' not distinguished. *''Populus nigra'' var. ''afghanica'' Aitch. & Hemsl. (syn. ''P. nigra'' var. ''thevestina'' (Dode) Bean). Southwest Asia; treated as a cultivar of ''P. nigra'' by many botanists,〔Germplasm Resources Information Network: (''Populus nigra'' var. ''thevestina'' )〕 and as a distinct species ''P. afghanica'' by others;〔Flora of Pakistan: (''Populus afghanica'' )〕 bark smooth, nearly white; leaves and shoots as subsp. ''caudina'' (see also cultivars, below). The subspecies ''betulifolia'' is one of the rarest trees in Great Britain and Ireland,〔Milne-Redhead, E. (1990). The B.S.B.I. Black Poplar survey, 1973-88. ''Watsonia'' 18: 1-5. Available (online ) (pdf file).〕〔Arkive: (''Populus nigra'' )〕 with only about 7,000 trees known, of which only about 600 have been confirmed as female.〔Cooper, Fiona (2006). ''The Black Poplar: Ecology, History and Conservation''. Windgather Press ISBN 1-905119-05-4〕 Several cultivars have also been selected, these being propagated readily by cuttings: *'Italica'. The true Lombardy poplar, selected in Lombardy, northern Italy, in the 17th century. The growth is fastigiate (having the branches more or less parallel to the main stem), with a very narrow crown. Coming from the Mediterranean region, it is adapted to hot, dry summers and grows poorly in humid conditions, being short-lived due to fungal diseases. It is a male clone.〔Bean, W. J. (1980). ''Trees and Shrubs Hardy in the British Isles'' Vol. 3. John Murray ISBN 0-7195-2427-X〕 As a widely selected species chosen by golf architects in the 1960s, it soon became apparent that the Poplar's very invasive roots destroyed land drainage systems. Decades later the same courses were removing Poplars stands wholesale. At around 40 to 50 years this short lived variety starts shedding branches and are very likely to be blown over in high winds, each successive tree lost exposing neighbouring trees creating a domino effect. *''Plantierensis'' group. A group of clones derived by crossing 'Italica' with ''P. nigra'' ssp ''betulifolia'' at the Plantières Nursery near Metz in France in 1884; they are similar to 'Italica' (and often mistaken for it) but with a slightly broader crown, and better adapted to the cool, humid climate of northwest Europe, where the true Lombardy poplar does not grow well. Both male and female clones are grown. This is the tree most commonly grown in Great Britain and Ireland as "Lombardy poplar".〔 *'Manchester Poplar'. A cultivar of subsp. ''betulifolia'' widely planted in northwest England. It is a male clone, and currently seriously threatened by Poplar Scab disease.〔Stace, C. A. (1971). The Manchester Poplar. ''Watsonia'' 8: 391-393.〕〔Arboricultural Information Exchange: (Manchester Poplar Disease )〕 *'Gigantea'. Another fastigiate clone, of unknown origin, with a rather broader, more vigorous crown than 'Italica'. It is a female clone.〔 *'Afghanica' (syn. 'Thevestina'). Most, if not all, specimens of the variety 'Afghanica' are of a single clone, and many botanists therefore treat it as a cultivar rather than a botanical variety. It is fastigiate, similar to 'Italica', but with a striking whitish bark; it also differs from 'Italica' in being a female clone. This is the common fastigiate poplar in southwest Asia and southeast Europe (the Balkans), where it was introduced during the Ottoman Empire period.〔 ==See also== *The Green Cathedral ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Populus nigra」の詳細全文を読む スポンサード リンク
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