The purpose of this work is to study the plantations of Populus × sibirica in the cities of Eastern Siberia, and to identify the phenotypic diversity of its qualitative traits in the region. To study the variability, 90 trees were examined, on which 1350 leaves were measured in the green spaces of the cities of Irkutsk, Bratsk and Krasnoyarsk. When analyzing the qualitative features, the following morphological markers were chosen: the shape of the leaf blade, its apex and base, the presence of basal glands, and petiole pubescence. In the past, Populus × sibirica was used very widely in the landscaping of the cities of Eastern Siberia, sometimes unjustifiably; at present, despite the extremely difficult ecological situation in the studied cities, it, as well as poplars in general are almost forgotten. Native species are extremely underused. The leaves of P. × sibirica are characterized by a predominantly ovoid blade shape, less often ovate-triangular. In the studied plantations, blades with a rounded wedge-shaped base and a pointed top predominate. At the endogenous level (within the individual), a number of characters (shape of the apex, base of the leaf blade, pubescence) do not vary – these characters are phenes for all taxa of the genus. According to the shape of the leaf blade, several morphs can be observed in the crown, but one of them always prevails. This pattern is also probably characteristic of the genus as a whole. The low levels of individual (intrapopulation) variability of traits and the extremely low differentiation of the studied plantations (1.1%) confirm the idea that the Siberian poplar is a cultivar and is probably represented in the studied cities of Eastern Siberia by a few clones.