AbstractIn Dutch rich fens, mid-successional stages dominated bySphagnum subnitensare rapidly being replaced by other vegetation, dominated byS. fallax.In both species growth was strongly reduced in more mineral-rich ground water and simulated river water, compared to growth in rain water.Both species were positively affected by added phosphorus supply, whereas added supply of nitrogen did not alter growth rates.Nutrient supply seemed to compensate for the intolerance to high mineral levels inS. fallax:nutrient addition stimulated growth in length in ground water and simulated river water. Such compensation was not found inS. subnitens.Growth in mixed culture positively affectedSphagnum subnitensand negatively affected its successorS. fallax.The success ofSphagnum fallaxin early stages of succession in more eutrophic fens may to some extent be explained by its tolerance to high mineral levels with increased nutrient supply.