Morphological differences among 20 populations of Carex viridula growing in different habitats in Poland were analysed based on examination of 365 specimens. Soil samples collected from each habitat were assayed for pH, organic matter, organic carbon, nitrogen, carbonates, and exchangeable elements (Ca, Mg, K, P). Statistical methods were used to detect patterns in morphological differences among the populations of C. viridula and to elucidate the effects of soil conditions on morphological characters. PCA and cluster analyses divided the specimens into two groups reflecting habitats differing in their soil conditions. A general pattern in the C. viridula morphology was found: habitats with soils of high contents of carbonates and exchangeable elements, and with pH exceeding 7.0, supported specimens usually having three or two (more seldom four) female spikes spaced widely apart, and long, usually peduncled, male spikes.