I. Aster tripolium is a very variable species of which a number of types have been described both on a morphological and ecological level. 2. In permanent plots along the height gradient in the salt marsh it appeared that differences in the A. tripolium subpopulations occur. 3. In the lowest zone of the marsh, dominated by Spartina anglica (Spartinion), the mean life expectancy of individual adult plants is relatively high but it is relatively low for seedlings. 4. In the higher zones of the marsh the mean life expectancy is relatively lower, but for the seedlings it is higher ( Puccinellion maritimae). 5. In the Spartina-zone individual A. tripolium plants have about twice the number of shoots as the plants from the other zones. 6. The plants from the Spartina zone produce per individual more generative shoots (absolute) but these have less capitula than elsewhere in the marsh. The number of ripe seeds per head is almost constant everywhere in the marsh. * Nomenclature follows Ooststroom S. J. van, 1977. Heukelsvan Ooststroom, Flora van Nederland, 19th ed., Wolters-Noordhoff, Groningen. ** Communication nr 301 of the Delta Institute for Hydrobiological Research. *** Acknowledgements: The authors are indebted to Dr. D. O. Wijnands, Mss. E. Miedema and M. Ham, who gathered numerous basic data during their undergraduate projects. They also wish to thank M r. J. A. van den Ende and Mr. A. A. Bolsius for the preparation of the figures and Mrs. M. J. van Leerdam for the typework.