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A tree said to be 90 to 100 ft high, but I have seen none much more than half that size in this country; bark of trunk smooth; young shoots and lower surface of the leaves covered with a thick, vividly white wool, which on the lobed leaves persists and keeps white until the fall of the leaf. Leaves variable; rounded to slightly heart-shaped at the base, blunt-pointed; on short twigs they are broadly ovate or almost round, irregularly wavy at the margins, 1 to 2 in. long; on vigorous shoots and young trees they are much larger, usually of maple-like form, being deeply three- or five-lobed and from 11⁄2 to 5 in. long, each lobe with a few large teeth. When the leaves first expand they are covered above with a loose white floss which falls away during the summer, leaving the upper surface very dark green and glabrous; stalk 1⁄2 to 11⁄2 in. long, woolly. Male catkins about 3 in. long; females 2 in. long.
A native of western and central Eurasia and N. Africa, occurring in Europe mainly in the eastern and southern parts. It is not a native of Britain, where it has been much confused with P. canescens. Its eastern limit is in Central Asia and the N.W. Himalaya.
The true white poplar very rarely attains a large size in this country, being short-lived. Large trees identified as white poplar are almost invariably P. canescens (q.v. for the points of difference). The degree of lobing on the long shoots of P. alba is variable on wild trees, being most marked in those of south-eastern Europe and in Asia, and least in the var. subintegerrima Lange, from S. Spain and N. Africa, which has leathery leaves that are scarcely lobed even on the strong shoots. The poplar which Dode named P. hickeliana belongs to this variety.
The foliage of P. alba sometimes turns a fiery red in the autumn, though yellow is the more usual colour. It is a useful tree in seaside localities, because of its tolerance of salt spray, and is also being increasingly used in roadside screens, etc.
Two trees in the University Parks, Oxford, appear to be true P. alba. Both are 8 ft in girth and just over 80 ft in height (1965). In Osterley Park, London, there is a specimen measuring 70 × 71⁄2 ft (1965).
As remarked on pages 299-300, the true white poplar is extremely rare in Britain in its normal form. The tree mentioned in the University Parks, Oxford, no longer exists and the Osterley Park tree has not been remeasured.
cv. ‘Pyramidalis’.- specimens: Kew, behind General Museum, 70 × 71⁄4 ft (1975); Valentine’s Park, Ilford, Essex, 66 × 53⁄4 ft (1984); University Botanic Garden, Cambridge, 62 × 81⁄4 ft (1982); Jephson Gardens, Leamington Spa, Warwicks., 70 × 71⁄4 ft (1981).
† cv. ‘Rocket’ (‘Raket’). – This is the result of a deliberate cross between a wild form of P. alba (seed-parent) and P. alba ‘Pyramidalis’ (‘Bolleana’), put into commerce in 1972. It is of erect growth and said to be an improvement on ‘Pyramidalis’.