Plant material from 42 common reed populations originating from various lakes and ponds in northwest Poland were investigated with respect to eight panicle traits and three peroxidase loci that were detected with electrophoresis. Genetic differences between populations were estimated based on allozyme frequencies. Electrophoretic data indicated that some populations contain an excess of heterozygotes, pointing to extensive gene flow, which is typical of panmictic, open-pollinated populations.