Untill 20 years ago seedlings of poplars were rarely found in the Netherlands. Nowadays, however, they are increasingly numerous, especially in the riverine area. This is probably due to poplar-planting activities, resulting in greater clonal diversity and better mixing of ♂ and ♀ clones with overlapping flowering periods as well for P. x canadensis as for P. nigra. Because backcrossess between P. nigra and P. x canadensis can be formed at sites with spontaneous regeneration, the identification of Poplars at these sites (especially the young trees) can give difficulties. The author gives a survey of the vegetative (and generative) differences.