In this paper the distributional pattern of Puccinellia fasciculata in the Netherlands is discussed. It is pointed out that three factors (inundation of considerable portions of the province Zeeland during World War II, extensive flooding of other parts in 1953, and the construction of new dikes) are responsible for the enormous increase in the area of distribution. It is to be expected that with the return to normal conditions the species will largely retreat to more normal distribution.