The Black Poplar (Populus nigra) appears to be so called not by reason of any blackness of leaf or bark, but because of the absence of any white or grey down on the underside of its leaves. Its bark is grey, like that of the species already mentioned, but readily distinguished from them by the great swellings and nodosities that mar the symmetry of its trunk. It is a tree of erect growth, fifty to sixty feet in height, with horizontal branches, and leaves that vary in shape from triangular and rhombic to almost circular, and in width from an inch to four inches. They have rounded teeth on the margins, which are at first also fringed, and in their young state the underside is silky. The flowers in the catkins of this and the next species are not so densely packed. Those of the male are two or three inches in length, and dark red in colour; their abundance before the tree has put out its leaves makes the male tree a conspicuous object. The female catkins
are shorter and do not droop. When the roundish capsules burst in May or June to distribute their seeds, the white cotton with which the latter are invested gives prominence to the female tree. The wood is chiefly used by the turner; in Holland, where it is extensively cultivated, it provides the material for sabots. The Black Poplar is not a native of this country, but it is generally distributed throughout Europe and Northern Asia. The date of its introduction is not known, but it has been here for many centuries, and is quite naturalized, springing up on river banks and in other moist situations. Some botanists regard it as only a variety of the Lombardy Poplar, but apart from the very different habit of the tree—not
by itself sufficient grounds for separation—there is the more important fact that the Black Poplar rarely produces suckers from its roots, whilst the Lombardy Poplar does so constantly. However, this is a point we can leave for the botanists to discuss; for the purposes of this book the two trees are sufficiently distinct to be treated separately.
The Lombardy Poplar (Populus fastigiata) is no more a native of Italy than of England. Its home is in the Taurus and the Himalayas, whence it has spread into Persia. Introduced into Southern Europe, it has become specially abundant along the rivers of Lombardy, and so in France and England it bears the name of that country. Lord Rochford introduced it to England from Turin in 1758. Its leaves are like those of the Black Poplar, but its branches, instead of spreading, all grow straight upwards, so that the fastigiate or spire shape of the tree is produced—a shape only found otherwise among coniferous trees, particularly in the Cypress, the Juniper and the Irish Yew. It is its form, great height (100 to 150 feet), and rapidity of growth that have led to its wide use here as an ornamental tree—in many cases as a mere vegetable hoarding to shut out some offensive view. Its growth is extremely rapid, especially during its first score of years, when it will attain a height of sixty feet or more, provided it be grown in good, moist (but not marshy) soil. Its wood is, of course, of little value, and is chiefly used for making boxes and packing-cases, where its lightness, combined with toughness and cheapness, is an advantage. The bark is rough and deeply furrowed, unlike the other species, and the trunk is twisted. Like the Black Poplar, it has smooth shoots, and the unopened buds are sticky. It is propagated in this country by suckers and cuttings. It is said that the first trees introduced were so obtained, and that they were all from male trees; consequently, that we have no female trees here, and seed production is impossible. If the female grows here, it is certainly very scarce. The bark has been used for tanning.
