Phragmites australis (Cav.) Trin. ex Steud. (common reed) is a widespread clonal species which shows variation in growth characteristics in the field, although the extent to which this variation is attributable to inherent differences between genetically distinct ecotypes has not been fully separated from differences due to variation in edaphic and hydrological conditions. By a combination of a trial using seed from different parents in four different populations and a replicated experiment at two different locations, this study distinguished some effects of genetic and phenotypic variation in plants grown from seed and rhizome segments. In both experiments, differences were found between plants taken from different populations, but grown under the same conditions. Although the site at which plants were grown had a strong influence on growth and productivity, plants from different populations did not necessarily react in the same way at the two experimental sites.
