Gametophores from mixtures of the closely relatedSphagnum fallax(H. Klinggr.) H. Klinggr. andSphagnum isoviitaeFlatberg, from two localities were clonally propagated in axenic culture and back transplanted from laboratory to field conditions, as well as reciprocally transplanted between the same localities. Genetic and environmental effects on leaf morphology were estimated to assess the taxonomic merit of these characters. Differences between populations exceeded between-taxon differences and could not be taken as evidence of two separate species. Plastic responses were apparent in the reciprocal transplant experiment, and a species-specific norm of reaction could be discerned in one character. Compared with the field experiments the species- and population-level genetic variances increased in the laboratory. This indicates that increased differences between species and populations were an artefact of experimental conditions, rather than caused by environmental effects opposing genetic effects on morphology in the field. Among-clone variances remained relatively stable across all experiments, as did residual variances indicating that the clonal propagation process did not elevate developmental noise. Contrasting responses between clonally propagated and field collected gametophores provide indirect evidence of changing levels of genetic and plastic variation throughout ontogeny.Key words: cultivation experiment, phenotypic plasticity, phenetics,Sphagnum, morphology.