Ramet distribution, leaf morphometry and elemental composition of Caltha palustris L. were studied along a hydrologic gradient in Nyárias marsh, N. E. Hungary, to identify patterns associated with water depth. Water-table height was linearly correlated with distance over most of the plant's distribution range. Caltha ramets were not dispersed uniformly but appeared in an aggregated pattern of a 12m scale. However, no clear relationship was found between water depth and the density of ramets, leaf number per ramet, aspects of plant performance (leaf blade and petiole dry weight), water status (water content of leaf parts), or leaf morphometry (lamina length and breadth, petiole length). Leaf size decreased towards both ends of the transect, and was highest at intermediate position. Contrastingly, foliar concentrations of several elements (e.g. Na, Mn, Cu) and especially the Fe: Mn ratio were strongly correlated with water-table height. Principal components analysis revealed two groups of elements: one discriminating between the lamina and the petiole but uncorrelated with the gradient (Ca, S, Fe, P, AI, K), and another not discriminating but positively correlated with the gradient (Na, Mn, Mg).The complex patterns of Caltha population traits in Nyárias demonstrate the ecologic importance of small-scale spatial (i.e. microtopographic) differences in wetlands. Besides water depth and duration per se, biotic factors such as gradients of standing crop, species richness or competition intensity may have intricate effects on single populations. Foliar Fe: Mn ratios, however, seem to be directly determined by water-table height and associated soil chemistry, thus can be a subtile indicator of wetland water conditions.