This study consist of a greenhouse competition experiment with the invasive species C. helmsii and the native (the Netherlands) L. uniflora. In this experiment, the development of C. helmsii (biomass, cover, nutrient composition) in competition with L. uniflora at different calcareous poor soil types (acid and buffered) and under different water tables (dry, inundated) was studied. The goal of this study was to understand the success or failure of C. helmsii development under different conditions, to gain insight in more effective and science-based restoration measures. This knowledge is highly valuable for restoration of soft water lakes in the Netherlands, but also in other European countries, where C. helmsii is posing a serious threat to native vegetation of EU concern.