Little has been recorded concerning the aspen and even less concerning the balsam poplar, because these trees are important only in natural stands and have been cultivated only exceptionally. The black poplar, however, has an interesting history.

The first poplars introduced from America and the East into France were intended only for ornamental purposes and as park trees; through grafting it became possible to propagate, rapidly and indefinitely, each of the types introduced, even single specimens.

Because of this, poplars trees soon became widely known and appreciated, whereas normally a long period of time, frequently a century, elapses between the introduction of a tree species by seed and its large-scale use in afforestation The rapid growth of these trees made possible early crossings of new species with the native Populus nigra. The first American poplars were introduced into Europe at the end of the eighteenth century. Henri-Louis Duhamel de Monceau in 1754, mentioned the results obtained in his poplar plantations, giving details concerning the ecology and technological qualities of the poplar and its timber

Hybrid poplars were planted at the same time, certain specimens of which are still alive; for example the P. euramericana f. serotina planted in 1752 in the Botanical Gardens of Nancy. This has attained a girth of 6.30 meters at 1.30 meters above ground.

Some of these hybrids were reimported into America by emigrants. Thus, at the beginning of the nineteenth century, François-André Michaux a naturalist and explorer in the eastern United States of America, was uncertain as to the classification of the black poplars found in the New York region. In his remarkable treatise on trees of North America ¹ reference is made to the "Swiss or Virginia poplar", a tree widely cultivated in Europe which, although it was not encountered, "is probably native to some part of America."

¹ Histoire des arbres forestiers de l'Amérique septentrionale. Paris, 1810-13, 4 vols.

During the nineteenth century, intelligent empirical experimentation led to the selection of a few valuable hybrids. These became an important feature of the French countryside and a valuable source of production. Gradually, these hybrids spread to other Western European countries.

A comprehensive study of poplars undertaken at the beginning of the twentieth century by the French botanist, Louis Albert Dode, failed to achieve practical results, because of its oversystematic treatment. Later, the work of such men as Edmond Henry, Candsdale, Gijsbertus Houtzagers, Regnier, and Piccarolo, contributed toward a reorientation of theoretical studies along practical lines.

Since 1947, most of the widely dispersed research has been co-ordinated within the International Poplar Commission under the chairmanship of Prof. Philibert Guinier.