Aronia x prunifolia has run wild in a number of reed marsh nature reserves in the western part of The Netherlands. Both in open Sphagnum-dominated communities and below the canopy of woodland the bushes can maintain themselves and reproduce, although performance in open vegetation seems to be better. On gaining dominance in the vegetation both the herb and the bryophyte layer become strongly reduced. From laboratory experiments environmental circumstances as encountered in reed marshes do not seem to affect the germination of Aronia adversely. No significant relations could be detected between the composition of the vegation and the amounts of nutrients available in the ground water at sites where Aronia was present. Only high cover percentages of Aronia were correlated with elevated amounts of NH*. The species may be found over a wide range from more or less oligotrophic conditions to slightly brackish and moderately eutrophic conditions. Factor analysis of the vegetation data produced no obvious relations with abiotic conditions. The density of Aronia and the structure of the vegetation dominated the first two factors, accounting for 47% of the variance in the data.