In central Europe the diploid, triploid and tetraploid cytotypes of the morphologically extremely variable S. telephium L. (X = 12) are syrapatric. The triploid plants are semisterile and most probably of hybrid origin. In mixed populations the triploid plants may give rise to an offspring consisting of aneuploid as well as diploid and/or tetraploid plants. Because the diploid and tetraploid cytotype each show almost the complete spectrum of morphological variation present within the S. telephium complex it is concluded that all taxa within this complex should be regarded as different expressions of a single though variable species.