A tree 100 ft or more high, with a rugged trunk 5 or 6 ft in diameter, often forming large burrs on the surface; young shoots glabrous and round; buds glutinous. Leaves variable, broadly diamond-shaped, triangular or ovate, 2 to 41⁄2 in. long; some are wider than they are long, others twice as long as they are wide, usually broadly tapered, sometimes straight across at the base, broad or slender-pointed, both surfaces green, quite glabrous, the translucent margins regularly and shallowly round-toothed; the teeth gland-tipped; stalk 3⁄4 to 21⁄4 in. long, compressed to a knife-like form. Catkins 2 to 3 in. long; anthers deep red; stigmas two in female flowers.
P. nigra (including its varieties) is of wide distribution in western Eurasia. The true black poplar is not very frequently seen now, having been supplanted to a great extent by the hybrids that have sprung up between it and the American P. deltoides. From that species it can be distinguished by the absence of marginal hairs and basal glands on the leaves; both these characters are also present in the hybrids in a greater or less degree (see further under P. × canadensis). As a timber tree P. nigra is not equal to the hybrids but as a tree for parks and gardens it has advantages. It is more leafy, has a more compact and shapely habit, branches more freely and finely, and does not grow so rampantly.
The most recent study of P. nigra, by W. Bugala, was published in Arboretum Kornickie, Rocznik (Yearbook) 12 (1967), pp. 45-219, with an English summary.
cv. ‘Afghanica’ (‘Thevestina’). – A tree resembling the Lombardy poplar in habit, but with a strikingly white bark which becomes dark and slightly furrowed on old trees; trunk rounded (not buttressed as in ‘Italica’). It also differs from ‘Italica’ in its foliage: the leaves on the short shoots are ovate, rounded at the base, acuminately tapered at the apex (deltoid, broadly cuneate at the base in ‘Italica’); those on the long shoots are longer than wide, rounded at the base (wider than long and truncate or slightly cordate at the base in ‘Italica’). It is a female clone and this is, of course, its chief distinction from ‘Italica’, which is male (P. nigra var. afghanica Aitch. & Hemsl.; P. thevestina Dode; P. afghanica (Aitch. & Hemsl.) Schneid.; P. nigra var. thevestina (Dode) Bean; P. usbekistanica Komar.
P. nigra ‘Afghanica’ arose by mutation from a race of the black poplar native to Central Asia, and is commonly cultivated there and over a wide area stretching from Kashmir to N. Africa, Turkey, and parts of south-eastern Europe (notably Bulgaria and S. Yugoslavia). Reports that the Lombardy poplar is to be found in Central Asia and the Middle East, etc., really refer to ‘Afghanica’, and the theory that the Lombardy poplar originated somewhere in this region stems from the same confusion. Whether the wild trees from which ‘Afghanica’ sprang should be regarded as a separate species or included in P. nigra is disputable. It is recognised as a distinct species by Bugala, who accepts for it the name P. usbekistanica Komar. But Dode’s name P. thevestina has priority and would be the valid name for the species even though it is founded on the cultivated clone ‘Afghanica’ and not on a wild plant.
This account is based largely on the work by Dr Bugala cited above, in which pages 164-82 are devoted to ‘Afghanica’, with numerous illustrations (English summary p. 213).
var. betulifolia (Pursh) Torr. P. betulaefolia Pursh; P. hudsoniana Michx. f. Downy Black Poplar. – A variety differing from the type in the young shoots, leaf-stalks, midrib, and main flower-stalk being downy (Bot. Mag., t. 2898).
This poplar, or rather its naming, has a curious history. It was first recognised by the younger Michaux early in the 19th century growing on the banks of the Hudson River, near Albany, New York State; he named it P. hudsonica. There is no doubt, however, that it was of European origin and is now considered to be the western race of P. nigra. It occurs wild in north-west France but whether it is truly a native of Britain is a question that has been much debated. It was certainly much planted in Britain in earlier centuries, before the coming of the hybrid black poplars, and specimens collected in England are common in the older herbaria. The survey now being conducted by the Botanical Society of Britain may allow a definitive conclusion to be reached.
The downy black poplar, like the type, produces great burrs on the trunk, and up to its middle age at least it is a neat, densely branched leafy tree, very much superior to the gaunt, rampant hybrids now almost exclusively planted. It grows well in a smoky atmosphere and was for that reason once commonly planted in the industrial midlands – whence the name ‘Manchester poplar’ used for P. nigra var. betulifolia in previous editions of this work. Recently, C. A. Stace examined 100 specimens from the Manchester area and found that all were male (Watsonia, Vol. 8, pp. 391-3), which suggests that the trees comprise a single clone. At least one, and probably all, the downy black poplars on Barnes Common, London, are also male.
cv. ‘Charkowiensis’. – A tree with ascending branches, forming an oblong or broadly pyramidal crown; bark lighter coloured than is usual in P. nigra. Young branchlets faintly downy. Female.
This poplar arose as a self-sown seedling in a nursery near Kharkov in Russia at the end of the last century and was put into commerce in western Europe by Späth in 1907. The Polish authority Bugala suggests that P. nigra ‘Afghanica’ enters into its parentage.
‘Charkowiensis’ was once much planted in Germany, especially in the Rhine valley. In this country it has not attracted much attention and has no special quality to commend it. The largest recorded specimen grows in the National Botanic Garden, Glasnevin, Dublin, and measures 80 × 63⁄4 ft (1966). There is a tree of 56 × 31⁄4 ft (1973) in the Forestry Commission collection at Alice Holt, planted in 1953.
cv. ‘Elegans’. – This poplar was apparently first distributed by the American firm of Ellwanger and Barry towards the end of the last century as P. elegans and is thought to be of the same parentage as ‘Plantierensis’. It was described as of pyramidal habit, broader than the Lombardy, with downy and red-tinted petioles and young stems. Whether it was one of the Simon-Louis clones renamed or of independent origin it is impossible to say. There is a poor example at Kew, very slender, with orange twigs.
cv. ‘Gigantea’. Giant Lombardy Poplar. – Resembling the common Lombardy, but of much broader habit and female. The origin of this poplar is unknown. According to Pourtet, a female fastigiate poplar was named P. gigantea by Dode and is cultivated to some extent in central France. But a poplar was received by Kew around 1880 as ‘the Giant Lombardy’ and it is almost certain that this is the tree listed as P. nigra var. pyramidalis gigantea in the early editions of the Kew Hand-list and mentioned as an example of a female Lombardy poplar in previous editions of the present work. The Kew tree, which grew near the Palace, was removed many years ago, but female trees of fastigiate but broad habit are still to be found in this country.
cv. ‘Italica’. Lombardy Poplar . – This well-known tree, the commonest of all fastigiate trees, differs from the type only in its slender tapering form and quite erect branches, and in its buttressed trunk (P. nigra var. italica Muenchh.; P. nigra var. pyramidalis Spach; P. fastigiata Desf.; P. dilatata Ait.).
The true Lombardy poplar is a male tree, propagated by cuttings, which began to spread from Lombardy into other parts of Europe early in the 18th century. It has been suggested that it is a distinct species native to Central Asia, but the Polish authority W. Bugala has pointed out that the fastigiate poplar of that region is not the Lombardy poplar but the very distinct ‘Afghanica’ (q.v.).
According to Aiton’s Hortus Kewensis, the Lombardy poplar was introduced to Britain from Turin by Lord Rochford, around 1758, but the Duke of Argyll may have planted it earlier in his collection at Whitton near Hounslow. It was in commerce by 1775.
The Lombardy poplar grows fairly fast when young and should attain 50 ft in height in twenty-five years, but it is not a long-lived tree. The largest recorded specimens are mostly 100 to 115 ft in height and rarely more than 11 ft in girth. The true Lombardy poplar is held in less regard than formerly, and the reason for its fall from grace is obvious enough, especially in country districts, where repeated attacks by the Marssonina fungus often kill the lower part of the crown, and also weaken the tree by causing premature leaf-fall. It is almost a century ago since the ill-health of the Lombardy was first remarked on, and it was then suggested that the clone was beginning to die of old age, but in fact it is disease that is the primary cause. To some extent the true Lombardy has been displaced by the healthier and more vigorous ‘Plantierensis’. This is all to the good, but ‘Plantierensis’ has no title to the name Lombardy poplar or ‘Italica’, and only confusion can result if it is sold as such.
As noted above, the true Lombardy poplar is a male clone. The so-called ‘female Lombardy poplars’ are almost certainly seedlings of typical P. nigra pollinated by ‘Italica’, and are generally less columnar than the male parent. Such trees have arisen in many places and on many occasions; see further under ‘Gigantea’ and ‘Vert de Garonne’. The same cross could, of course, also produce male trees but these, being less obviously distinct from ‘Italica’, have attracted less attention. For the cross between P. nigra ‘Italica’ and P. nigra var. betulifolia, see ‘Plantierensis’.
Fastigiate forms of black poplar have also arisen from P. nigra var. pubescens crossed with P. nigra ‘Italica’. According to Bugala, trees of this parentage occur in Tuscany in both sexes; they are of dense, slender habit and are easily distinguished from ‘Plantierensis’ by the very dense and persistent down on the short shoots and inflorescences. The same authority states that crosses between ‘Italica’ and ‘Afghanica’ occur in those parts of Europe where both these fastigiate clones are cultivated.
cv. ‘Plantierensis’. – Resembling the Lombardy poplar in habit though sometimes broader and with downy young leaves and stems (P. nigra var. plantierensis Schneid.; P. plantierensis Dode; P. fastigiata plantierensis Simon-Louis).
This poplar originated in the nursery of Messrs Simon-Louis, Plantières, near Metz, and is thought to have sprung from P. nigra var. betulifolia, pollinated by ‘Italica’. Apparently some fifteen self-sown seedlings were found, of which at least two, one male, one female, were propagated and put into commerce in 1884-5. The name ‘Plantierensis’ is therefore not clonal.
Deriving as it does from the Atlantic race of P. nigra, ‘Plantierensis’ grows more vigorously in our climate than the true Lombardy poplar, which it has to some extent replaced in cultivation. In the course of his survey of the black poplar and its hybrids in Britain, G. S. Cansdale received eighteen specimens of true Lombardy to forty-five of ‘Plantierensis’ and remarked in his report: ‘Both varieties commonly pass under the name “Lombardy Poplar” and are distinguished only by botanists, so that the superior numbers of the latter (“Plantierensis”) may well be due to its representing a more vigorous stock.’ (The Black Poplars (1938), p. 29.) In fact, the two are distinguishable without examination of the foliage, since ‘Plantierensis’ is a much leafier tree, with a denser crown.
More recently, Miles Hadfield and Alan Mitchell have found that a fastigiate black poplar common in the Severn valley from the Hereford area as far north as Leighton has downy twigs. The trees are leafier than the Lombardy, hold their foliage until later in the autumn, and are somewhat broader-topped. Examples are: Wellington Heath, Ledbury, 104 × 131⁄2 ft (1966); Leighton Park, Montgom., 110 × 153⁄4 ft and 100 × 163⁄4 ft (1964); Croome Court, Worcs., 92 × 14 ft (1964). These trees exceed in girth any example of true Lombardy measured in recent years. Whether they represent the ‘Plantierensis’ of Simon-Louis or some other variety of similar origin it is impossible to say. Despite their large girth, the oldest are not necessarily more than eighty years old, but if they do derive from Plantières, they must have been planted very soon after Simon-Louis put their variety into commerce. Those trees on which catkins have been seen are male.
var. pubescens Parl. P. nigra subsp. caudina (Ten.) Bugala; P. caudina Ten.; P. hispida Hausskn. – Stems and inflorescence axes densely hairy, also, to a varying degree, the petioles and the veins on the undersurface of the leaves. S. and S.E. Europe and N. Africa. The hairs on the stems are much denser and more persistent than in var. betulifolia.
cv.’ Vereeken’. – A fast-growing male clone with a columnar-conic crown, raised in Belgium and of recent introduction. An example in the Forestry Commission collection at Alice Holt, pl. 1954, measures 64 × 33⁄4 ft (1973).
cv. ‘Vert de Garonne’. – In the valley of the Garonne and its tributaries, and in the Rhone valley, there is found a race of more or less fastigiate black poplars, the origin of which is uncertain; it may be spontaneous or, more probably, the result of pollination of native trees by ‘Italica’. Some of these trees have been propagated vegetatively, notably ‘Vert de Garonne’, a female tree of good habit rather broader than ‘Italica’ and more leafy. Other clones that have been named are: ‘Blanc de Garonne Seihl’ (male, fairly broad); and ‘Sarrazin de Seihl’ (narrowly fastigiate, sex not ascertained). For this information we are indebted to Pourtet’s work La Culture du Peuplier (1957).
var. viadri (Rüdiger) Aschers. & Graebn. P. viadri Rüdiger – An obscure variety, described in 1891 from trees growing on the Oder near Frankfurt (Viadrus is the Latin name for the Oder). It is said to occur in both sexes, and to be of fastigiate habit, though one tree received at Kew from Rüdiger proved to be ordinary P. nigra.